Small,Ocean,Sea,Waves,On,Sandy,Beach,With,Sunrise,Sunset.

<p>You've likely heard that the moon is responsible for tides on Earth, but have you ever actually thought about why? While the moon has the biggest effect on Earth's tides, the sun and the ocean's shape also have effects that increase or decrease the tide. The effects of the moon on Earth's tides are called moon tides. Moon tides are the main focus of this article.&nbsp;</p>



<figure class="wp-block-image size-large is-style-default"><img src="https://www.earth.com/wp-content/uploads/2022/09/moon_10big_stock-1024x683.jpg" alt="" class="wp-image-1912202"/></figure>



<h2 id="h-moon-tides-from-the-moon-orbiting-the-earth">Moon Tides from the Moon Orbiting the Earth</h2>



<p>Everything in space exerts gravity on everything else. Since the moon is the closest celestial body to Earth, it exerts the greatest force on the Earth's oceans. The force of the&nbsp;moon's gravity pulls both the Earth and the water on Earth's surface closer to the moon. When water is pulled towards the moon the tide goes up. Whatever part of the Earth is closest to the moon experiences the most intense lunar gravity, and therefore the most intense moon tide. But the gravitational pull of the moon doesn't stop there! The moon also pulls the Earth slightly towards it, pulling the side of the Earth closest to the moon with the most force, and the side of the Earth furthest away from the moon with the least amount of force. The water on the side of the Earth furthest from the moon experiences the least amount of lunar gravity.&nbsp;</p>



<p>There are two high tides each day. As the Earth completes its 24-hour, day-long rotation, the side of the Earth which is closest to the moon constantly changes. This is why a high tide happens every 24 hours (actually, it's 24 hours and 50 minutes, but more on that later).</p>



<figure class="wp-block-image size-large"><img src="https://www.earth.com/wp-content/uploads/2022/02/shutterstock_2064415841.jpg" alt="" class="wp-image-1904626"/><figcaption>A graph shows the height of the tide over a 24 hour period. <a href="https://www.shutterstock.com/g/pijitra-phomkham">PIJITRA PHOMKHAM</a>/<a href="http://shutterstock.com">Shutterstock</a>.</figcaption></figure>



<h3 id="h-the-second-high-tide">The Second High Tide</h3>



<p>Each day there is a second, lesser high tide. This second high tide occurs on the side of Earth furthest from the moon. Initially, that doesn't seem to make much sense, right?</p>



<p>While the moon pulls all the water on Earth towards it, it also pulls the Earth slightly towards the moon. Since the water furthest from the moon experiences little lunar gravity, it is being pulled less than the rest of the Earth. This means that, because the water farthest from the moon gets pulled the least, the water is higher compared to the Earth.</p>



<p>Additionally, as the Earth and moon spin around each other, the water furthest from the moon experiences centripetal force. This means that the water furthest from the moon is being spun as the Earth travels around the moon with more force than the water closest to the moon. Together, the centripetal force and the difference in gravity between the sides of the Earth facing the moon create a tidal bulge on the opposite side of Earth from the moon.</p>



<h3 id="h-low-moon-tides">Low Moon Tides</h3>



<p>The areas of the ocean halfway between the side of the Earth closest to the moon and the side furthest away experience low tides. These low tides occur because neither the lunar gravity is particularly strong, nor the effect from the centrifugal force. Low tides occur halfway between high tides, or about every six hours.</p>



<p>This is how the moon tides work on a day-long period.</p>



<figure class="wp-block-image size-large"><img src="https://www.earth.com/wp-content/uploads/2022/02/shutterstock_1038196303-1024x929.jpg" alt="" class="wp-image-1904629"/><figcaption>A diagram demonstrating how the sun interacts with the moon to make spring and neap tides. <a href="https://www.shutterstock.com/g/marina-durante">Anna L. e Marina Durante</a>/<a href="http://shutterstock.com/">Shutterstock</a>.</figcaption></figure>



<h2 id="h-phases-of-the-moon-impact-moon-tides-sort-of">Phases of the&nbsp;Moon&nbsp;Impact Moon Tides (Sort Of)</h2>



<p>Moon tides also depend on a month-long time scale. When the moon is full and new, Earth experiences spring tides. When the moon is half full (a waxing or waning gibbous), the Earth experiences neap tides. Neap tides are weak, meaning the difference between the high and low tides is small. Spring tides, on the other hand, are strong. Spring tides and neap tides, while correlated with the moon, are technically not moon tides; they are solar tides.&nbsp;</p>



<p>The sun also exerts gravity on Earth and contributes about half as much to the tides as the moon. The effect of the sun on tides is called solar tides. Acting together, the moon and sun create large tidal forces.</p>



<p>When the moon is new, it is between the Earth and the sun. This means the lined-up forces from the moon and the sun add together to create an extra strong pull. When the moon is full, it is on the opposite side of the Earth from the sun. Since the sun and moon each pull on an opposite side of Earth, this also creates spring tides.</p>



<p>Bonus fun fact: When three celestial bodies are lined up they are in 'syzygy.' Can you believe a word like that exists?</p>



<figure class="wp-block-image size-large"><img src="https://www.earth.com/wp-content/uploads/2022/09/moon_neap-tide_nasa.gif" alt="" class="wp-image-1912203"/></figure>



<p>When the moon is half full, the moon and sun make a right&nbsp;angle, with the Earth in the middle. In this position, the moon tides and sun tides interfere with each other, creating small neap tides.&nbsp;</p>



<h3 id="h-the-moon-s-orbital-period-impacts-moon-tides">The Moon's Orbital Period Impacts Moon Tides</h3>



<p>It takes the moon 29.5 days to completely orbit the Earth or to go from full moon to full moon. This is called the moon's "synodic" or lunar&nbsp;month. Kind of like how the hour and second hand on a clock move at different rates, the moon slightly outpaces the Earth's 24-hour rotation. This means that the moon will be in slightly further along in the sky once the Earth does its complete 24-hour rotation. If you divide 24 hours by 29.5 days (the moon's orbit around Earth), you get about 50 minutes. This is why lunar tides are 24 hours 50 minutes and why the time of the high tide gets later by 50 minutes every day. </p>



<figure class="wp-block-image size-large"><img src="https://www.earth.com/wp-content/uploads/2022/02/shutterstock_120511270.jpg" alt="" class="wp-image-1904631"/><figcaption>This diagram demonstrates a new moon approximately at the apogee and the full moon at the perigee of the moon's orbit.<br><a href="https://www.shutterstock.com/g/redsapphire">Redsapphire</a>/<a href="http://shutterstock.com/">Shutterstock</a>.</figcaption></figure>



<h2 id="h-the-shape-of-the-moon-s-orbit-impacts-moon-tides">The Shape of the Moon's Orbit Impacts Moon Tides</h2>



<p>Not only does the moon orbit around Earth, but the moon also moves through its own, elliptical orbit. When the moon is closest to Earth in its ellipse, it exerts more gravity and, therefore, higher tides. This position is called the perigee. In contrast, when the moon is further away from Earth in its elliptical orbit, tides are unusually small. This position is called the apogee.</p>



<p>This elliptical orbit does not match the moon's&nbsp;orbit around the Earth. As mentioned above, the moon's orbit around the Earth, or synodic month, is 29.5 days. The elliptical orbit, or anomalistic month, is 27.5 days. This means that each time the moon is full, it will be in a slightly different place within its elliptical orbit.&nbsp;</p>



<figure class="wp-block-image size-large"><img src="https://www.earth.com/wp-content/uploads/2022/02/shutterstock_1586532991.jpg" alt="" class="wp-image-1904635"/><figcaption>This diagram drastically accentuates the elliptical nature of the moon's orbit. The moon's orbit is essentially round with just a tiny oval squish to it. <a href="https://www.shutterstock.com/g/renklerinkafasi">renklerin kafasi</a>/<a href="http://shutterstock.com/">Shutterstock</a>.</figcaption></figure>



<p>When the moon is full or new and in its perigee, the moon is a&nbsp;<a href="https://www.earth.com/news/super-worm-moon-tonight/" target="_blank" rel="noreferrer noopener">supermoon</a>. The gravity of the combined sun and moon, plus the closer-than-usual position of the moon make for exceptionally high tides.&nbsp;</p>



<h3 id="h-the-earth-s-orbit-is-also-elliptical">The Earth's Orbit is Also Elliptical</h3>



<p>Interestingly, the Earth also has a slightly elliptical orbit around the sun. Similarly to the moon's orbit, the tides are larger when the Earth is closest to the sun, around the New Year. The tides are smaller in early July, when the Earth is furthest from the sun.&nbsp;</p>



<h3 id="h-the-moon-has-an-even-longer-orbit">The Moon Has An Even Longer Orbit</h3>



<p>The moon also has a wobble in its orbit that changes the magnitude of tides on 18.5 year scale. This wobble will make tides higher than usual&nbsp;<a href="https://www.earth.com/news/the-moons-wobbles-will-cause-a-surge-in-coastal-flooding/" target="_blank" rel="noreferrer noopener">in the 2030s</a>.&nbsp;</p>



<h2 id="h-the-shape-of-the-continents-and-ocean-floor">The Shape of the Continents and Ocean Floor</h2>



<p>Not all tides are created equal. In the Bay of Fundy in Canada, the difference between high and low tide is&nbsp;<a href="https://bayoffundytourism.com/worlds-highest-tides/times/" target="_blank" rel="noreferrer noopener">40-50 feet</a>. Many coastal areas only have a few feet of difference between high and low tide.</p>



<p>While not the scope of this article, the shape of Earth's oceans, coastline, and ocean floor all contribute to the vast differences between tides in different coastal areas.</p>



<figure class="wp-block-image size-large"><img src="https://www.earth.com/wp-content/uploads/2022/02/shutterstock_2049610358.jpg" alt="" class="wp-image-1904636"/><figcaption>This line of seaweed was left when the high tide retreated back down the beach. <a href="https://www.shutterstock.com/g/elmar-langle">Elmar Langle</a>/<a href="http://shutterstock.com/">Shutterstock</a>.</figcaption></figure>



<h2 id="h-combining-the-factors-to-make-the-biggest-moon-tide">Combining the Factors to Make the Biggest Moon Tide</h2>



<p>The highest tide would happen when many of these factors occurred at the same time. First, the moon must be a&nbsp;<a rel="noreferrer noopener" href="https://www.earth.com/news/tonights-super-moon-coincides-with-a-total-lunar-eclipse/" target="_blank">supermoon</a>, where the moon is new and at its perigee. If the super moon this happened around the New Year, when Earth is closest to the sun, it would be a massive tide. If this combined with a storm, heightened sea levels from climate change, and the moon's 18.5 year wobble, it would likely be the highest water level possible. Tides such as this pose great issues to low-lying coastal areas, which are prone to&nbsp;<a rel="noreferrer noopener" href="https://www.earth.com/news/global-warming-will-greatly-increase-flood-related-displacement/" target="_blank">devastating tidal flooding</a>.&nbsp;</p>



<p>Moon tides have lead to the evolution of special tidal critters and all sorts of interesting animal behavior. Next time you are at the beach make sure to pay attention to the moon, how the time and height of the tides change from day to day, and how the birds, and fish use the tides to their advantage. </p>



<p>Check us out on&nbsp;<a href="https://www.earth.com/earthsnap/">EarthSnap</a>, a free app brought to you by Eric Ralls and Earth.com.</p>

What are Moon Tides?

You've likely heard that the moon is responsible for tides...

Vombatus,Ursinus,-,Common,Wombat,In,The,Tasmanian,Scenery,,Eating

<p>A wisdom of wombats makes a thousand cubed poops in a day. &nbsp;Believe it or not, that is a factually and grammatically correct sentence. Yes, a group of wombats is called a wisdom. And yes, they do indeed each poop about 100 distinct cubes each per day. How cube-ish are the cubes? Take a look for yourself!</p>



<figure class="wp-block-image size-large"><img src="https://www.earth.com/wp-content/uploads/2021/11/shutterstock_1256653177.jpg" alt="" class="wp-image-1898942"/><figcaption>A cubed piece of wombat poop lies on the ground. <a href="https://www.shutterstock.com/g/mandycreighton">Mandy Creighton</a>/Shutterstock.com</figcaption></figure>



<p>They are pretty good cubes, right? It would take a significant amount of effort to sculpt cubes that are cube-like out of clay. But wombats are natural sculptors and make the cubes automatically. In fact, wombats are the only animals<em>&nbsp;in the world</em>&nbsp;that poop cubes. Until just a few years ago, scientists had no idea how they made this square scat.&nbsp;</p>



<h2 id="h-what-are-wombats">What Are Wombats?</h2>



<p>Wombats are the world's largest burrowing mammal. Wombats can weigh up to 80 pounds and are about 3 feet long when fully grown. In the wild, these fuzzy creatures can live to be almost 30 years of age! Wombats are herbivores. They eat a relatively mundane diet of grasses and other grass-like plants. Wombats incisors, a type of tooth, never stop growing. This constant growth means they need to chew on plenty of tough stuff every day to shave off their teeth as they grow.&nbsp;</p>



<p>These burrowing cuties are a type of marsupial, which means they give birth to undeveloped young wombats who grow inside the mother's&nbsp;pouch. Unlike most marsupials, the wombat's pouch faces towards its hind legs. This unique evolutionary adaptation prevents the pouch from filling up with dirt while the wombat digs in the soil with its front paws.&nbsp;</p>



<figure class="wp-block-image size-large"><img src="https://www.earth.com/wp-content/uploads/2021/11/shutterstock_1700659525.jpg" alt="" class="wp-image-1898943"/><figcaption>A baby wombat peeks out of its mother's pouch, looking out through the mother's hind legs. <a href="https://www.shutterstock.com/g/Jonas_Boernicke">Jonas Boernicke</a>/Shutterstock.com</figcaption></figure>



<p>Wombats are productive diggers. A hard-working wombat can excavate three feet of tunnel in a single evening. As you can imagine, these networks of burrows can become extensive. Underground temperatures remain much more stable than air temperatures, so wombats hide in their burrows during the day to escape the searing Australian sun. &nbsp;</p>



<p>Wombats are mostly nocturnal creatures, making them hard to see in real life.</p>



<h3 id="h-where-do-wombats-live">Where do Wombats Live?</h3>



<p>All marsupials, which also include&nbsp;<a rel="noreferrer noopener" href="https://www.earth.com/news/scientists-ponder-how-to-curb-kangaroo-flatulence/" target="_blank">kangaroos</a>, Tasmanian devils, and&nbsp;<a rel="noreferrer noopener" href="https://www.earth.com/news/deadly-koala-virus-passed-from-mothers-to-their-joeys/" target="_blank">koalas</a>, are endemic to Australia and the Americas. Wombats can inhabit a wide variety of habitats within Australia, from arid grasslands to cool alpine zones, to&nbsp;eucalypt woodlands. Wombats need a healthy ecosystem of native Australian grasses nearby to thrive.&nbsp;</p>



<h3 id="h-the-three-different-kinds-of-wombats">The Three Different Kinds of Wombats</h3>



<p>There are three species of wombats alive today. Differentiating the three depends on how hairy their nose is and where they live. The most common wombat is the bare-nosed wombat (<em>Vombatus ursinus</em>). The bare-nosed wombat lives near the coast in southeastern Australia in the provinces of New South Wales, Victoria, Tasmania, and southern Queensland. This also happens to be where nearly all the people in Australia live.&nbsp;</p>



<p>The southern hairy-nosed wombat(<em>Lasiorhinus latifrons</em>) wombat lives in the province of South Australia in south-central Australia.&nbsp;</p>



<p>Northern hairy-nosed wombat (<em>Lasiorhinus krefftii</em>) only lives in one small area in Queensland, called Epping Forest National Park.&nbsp;</p>



<h3 id="h-unfortunately-these-cute-marsupials-are-in-trouble">Unfortunately, These Cute Marsupials Are in Trouble</h3>



<p>Wombats were, and in some cases still are, considered agricultural pests across Australia. Being the world's largest burrowing mammal comes with consequences. These critters stir up substantial amounts of dirt and eat plenty of food, causing farmers and ranchers much frustration. Wombats can also destroy fences, letting invasive rabbits into areas people try to keep them out of. As a result, wombats were routinely killed as vermin across Australia throughout the 1900's. Still today the common wombat is not protected in the province of Victoria.&nbsp;</p>



<p>The&nbsp;<a href="https://www.iucnredlist.org/species/11343/21959050" target="_blank" rel="noreferrer noopener">IUCN</a>&nbsp;lists the northern hairy-nosed wombat is among the most endangered mammals on Earth. At one point in the early 2000's the population of breeding adults was just over 100. Predation by dingoes (wild dogs), competition for grass forage by non-native rabbits, and overgrazing by cattle and sheep drove this wombat population way down. Drought induced by climate change makes life additionally difficult for not only wombats,&nbsp;<a href="https://www.earth.com/news/severe-drought-australia-wildlife/" target="_blank" rel="noreferrer noopener">but all sorts of wildlife across Australia</a>.&nbsp;</p>



<p>In 2000 the Australian government installed a dingo-proof fence around the entirety of the northern-hairy-nosed wombat habitat. Their numbers have been slowly improving since then, and are now thought to be over 300 individuals. Still, this wombat remains a critically endangered species at risk of extinction due to wildfire or diseases like mange.&nbsp;</p>



<p>The southern hairy-nosed wombat isn't quite as imperiled as its northern neighbor, but is still listed as near-threatened. The common wombat is classified as "least concern.," but scientists are concerned by that species's population's downward trend.&nbsp;</p>



<figure class="wp-block-image size-large"><img src="https://www.earth.com/wp-content/uploads/2021/11/shutterstock_580673665.jpg" alt="" class="wp-image-1898945"/><figcaption>A small collection of cubic wombat scat. <a href="https://www.shutterstock.com/g/Pixelheld">Pixelheld</a>/Shutterstock.com</figcaption></figure>



<h2 id="h-why-is-wombats-poop-cubic">Why is Wombats' Poop Cubic?</h2>



<p>As with so much in nature, we don’t know for certain why wombats poop cubes. However, we have a better idea now than we did just a few years ago.</p>



<p>One (debunked) folksy theory is that cubed poop is a superior shape to help wombats mark their territories. Why? Because cubes stack and don’t roll off of rocks. Can’t you imagine it? A pudgy wombat meticulously builds a menacing pyramid of cubed poops to alert other wombats to “stay away”. Or a wombat purposefully poops on slick rocks gleefully knowing their poop doesn’t roll right off. These theories aren’t wrong,&nbsp;<em>per se</em>, but there are probably more likely reasons for the evolution of cubed poop. There are so many animals that use their poop to mark their territories, but wombats are to only animals in the world with square poop.</p>



<h3 id="h-the-new-theory-of-wombat-poop">The New Theory of Wombat Poop&nbsp;</h3>



<p>Researchers Patricia Yang and David Hu <a href="http://hu.gatech.edu/wp-content/uploads/2021/01/Hu21-wombat.pdf" target="_blank" rel="noreferrer noopener">published a paper</a> that opened the world's eyes to the inner workings of the wombat. They found that the wombat's unique intestine was responsible for the cubic wombat poop. Instead of being extruded, like clay from a mold or pasta from a pasta-maker, the poop gets shaped by wombats' long intestines over the course of days. </p>



<p>Wombat intestines are about 10 times the length of their bodies. These long intestines help the critters extract an impressive amount of water from the food they eat. Wombats can live in incredibly arid environments. In fact, they barely need to consume water because their super intestines can squeeze all the water a wombat needs out of the plants it eats. Other desert mammals, such as the adorable <a href="https://www.earth.com/video/kangaroo-rat-spotted/" target="_blank" rel="noreferrer noopener">kangaroo rat</a>, have similar adaptations. Some scientists think that the process of forming cubes helps the wombat extract more water from its food.</p>



<p> Yang and Hu took the long intestines of a roadkill wombat and filled the intestines with a long balloon. They then inflated the balloon inside the intestine. By comparing how the balloon stretched the wombat intestines to how balloons stretched other animals' intestines, the researchers unlocked a crucial aspect of the cubic poop mystery. </p>



<p>Instead of being uniformly tight as other animals' intestines, wombat intestines have four 'strips' that run the length of the organ. Two of these strips contract more vigorously and two of the strips don't contract less vigorously. These strips alternate, so that a cross-section of the wombat intestine would show vigorous-regular-vigorous-regular strips of the intestine. For some complicated, fluid-dynamics and physics reasons, these contractions turn the cylindrical poop into cubic poop, all within a cylindrical intestine. Apparently, the poop only becomes cubic in <a href="https://pubs.rsc.org/en/content/articlelanding/2021/sm/d0sm01230k?&amp;_ga=2.96994969.788068061.1636953912-1075994723.1634916763#!divAbstract" target="_blank" rel="noreferrer noopener">the last 20%</a> of the wombat intestine. </p>



<h3 id="h-the-surprising-implications-of-wombat-poop-research">The Surprising Implications of Wombat Poop Research</h3>



<p>The researchers note that understanding wombat poop can help us in manufacturing and cancer diagnosis. Figuring out new ways of extruding plastics can help manufacturers mold different shapes. Colon cancer has been known to change the interior of intestinal walls. Now that we understand how changes in intestinal walls can change the shape of poops, researchers think they may be able to detect colon cancer earlier by observing human fecal samples. It's always difficult to see how some research will be used for wildly different purposes!</p>



<p>Wombat poop is a strange wonder of the natural world. If you ever have the opportunity to wander around wombat habitat, keep an eye out for this charming, cubic feces!</p>



<p>Check us out on <a href="https://www.earth.com/earthsnap/">EarthSnap</a>, a free app brought to you by Eric Ralls and Earth.com.</p>

Wombats and the Mystery of Cubed Poop

A wisdom of wombats makes a thousand cubed poops in...

<p>Just as humans have polluted planet Earth's oceans, lands, and air, we have begun to also pollute the Earth's orbit with space junk. Every time humans have launched a rocket up into space, part of it remains there. Over the course of thousands of launches, this trash adds up and has catastrophic potential.</p>



<h2 id="h-why-is-space-junk-a-problem">Why Is Space Junk a Problem?</h2>



<p>Any human-made, non-functional object in the Low Earth Orbit (LEO) is considered space junk. LEO is anywhere from 100 miles to 600 miles above Earth's surface. This is <a href="https://www.esa.int/ESA_Multimedia/Images/2020/03/Low_Earth_orbit" target="_blank" rel="noopener">the zone</a> where the International Space Station, satellites, and other space projects exist. Due to the gravity of Earth, objects in the LEO orbit around our planet.</p>



<p>While space in its entirety is unimaginably vast, the LEO isn't <em>all that</em> huge. Consider that humans have launched thousands of rockets into space to date. Each of those rockets has a <a href="https://www.earth.com/earthpedia-articles/what-is-a-rocket-most-famous-launches/" target="_blank" rel="noopener">payload, </a>which is the stuff humans are trying to get into space (often satellites). These rockets also typically have upper stages, which are the last part of the rocket that propels the payload into the LEO. These upper stages, unlike the lower stages which drop away in Earth's atmosphere, remain in space.</p>



<figure class="wp-block-image alignnone wp-image-1887854 size-full"><img src="https://www.earth.com/wp-content/uploads/2021/01/shutterstock_1182292486.jpg" alt="space junk" class="wp-image-1887854"/><figcaption>A hypothetical space trash ring around Earth. <a href="https://www.shutterstock.com/g/Dotted+Yeti">Dotted Yeti</a>/Shutterstock.com</figcaption></figure>



<h3 id="h-the-consequences-of-a-collision-in-space">The Consequences of a Collision in Space</h3>



<p>All of these upper stages and satellites from space missions remain in LEO. They don't disappear once sent into space. In fact, there are over <a href="https://www.nasa.gov/mission_pages/station/news/orbital_debris.html" target="_blank" rel="noopener">20,000 pieces</a> of man-made material in LEO that are larger than a softball. Altogether, this space trash weighs <a href="https://www.floridatoday.com/story/tech/science/space/2020/12/23/nasa-concerned-spaces-growing-trash-problem/6544727002/" target="_blank" rel="noopener">over 6000 tons</a>. This space junk orbits Earth <a href="https://www.esa.int/ESA_Multimedia/Videos/2019/02/Distribution_of_space_debris_in_orbit_around_Earth/(lang)" target="_blank" rel="noopener">all over the place</a>. Since these objects travel over <a href="https://www.nasa.gov/mission_pages/station/news/orbital_debris.html" target="_blank" rel="noopener">17500 miles per hour</a> (about five miles <em>per second</em>), any collision would be enormously powerful.</p>



<p>For example, a paint chip collided with a window on a space shuttle mission. NASA decided they needed to <a href="https://www.nasa.gov/mission_pages/station/news/orbital_debris.html" target="_blank" rel="noopener">replace the window</a> because of the damage the fleck of paint caused. We think there are over half a million pieces of space junk as big as this fleck of paint. Windows of the International Space Station (ISS) have also been damaged by paint flecks.</p>



<p>If one of the larger pieces of space trash hit the ISS, the results would be catastrophic. NASA keeps a database of all the known pieces of space junk larger than 4cm across and had to alter the course of the ISS three times in 2020 to avoid potential collisions with space junk. The ISS always has humans on board, so any potential collision with space trash is harrowing.<em>&nbsp;</em></p>



<h3 id="h-kessler-syndrome-the-doomsday-of-space-exploration">Kessler Syndrome - The Doomsday of Space Exploration</h3>



<p>While paint flecks may seem harmless enough, space junk could become really bad really quickly. Imagine one of the softball-sized pieces of junk hits a large, old upper stage of a rocket floating in LEO. The softball-sized debris would shatter the upper rocket stage into thousands of pieces of smaller space trash. This increased number of space junk objects would exponentially increase the odds of more collisions. The <a href="https://www.earth.com/earthpedia-articles/what-is-the-kessler-syndrome/" target="_blank" rel="noopener">Kessler Syndrome</a> is the point at which these collisions happen as a chain reaction, with each collision making the next one increasingly likely. <strong>At some point during the Kessler Syndrome, it would be too dangerous for us to send humans to space.</strong></p>



<h3 id="h-humans-send-more-junk-to-space-every-year">Humans Send More Junk to Space Every Year</h3>



<p>As space flight and satellite technology become <a href="https://www.earth.com/earthpedia-articles/how-many-satellites-in-space-do-we-know-about/" target="_blank" rel="noopener">increasingly affordable</a>, more private companies are sending satellites into orbit. <a href="https://www.nasa.gov/mission_pages/cubesats/overview" target="_blank" rel="noopener">Cubesats</a>, which are small, 1-liter sized satellites are easy for private companies to create and get into orbit. Companies that focus on communications, mapping, and remote sensing are all sending cubesats into LEO. In 2020, humans sent <a href="https://www.cnbc.com/2020/06/19/arianespaces-vega-rocket-challenging-spacex-rocket-lab-in-the-small-satellite-market.html" target="_blank" rel="noopener">400 cubesats</a> into LEO. Compared to the <a href="https://astroscale.com/space-debris/" target="_blank" rel="noopener">9,000 satellites</a> launched in the entirety of space exploration, this is a marked increase. If humans continue to send this amount of stuff into space, the space trash problem will get worse and worse. If billionaires like Elon Musk, Richard Branson, and Jeff Bezos get their way with daily <a href="https://www.earth.com/earthpedia-articles/top-3-biggest-private-space-companies/" target="_blank" rel="noopener">private space flights</a>, <strong>the problem may become unsolvable.</strong></p>



<figure class="wp-block-image alignnone wp-image-1887856 size-full"><img src="https://www.earth.com/wp-content/uploads/2021/01/shutterstock_1339563719.jpg" alt="cubesat trash" class="wp-image-1887856"/><figcaption>A graphic of a cubesat. Before unfolding, this satellite was about the size of a Nalgene water bottle. <a href="https://www.shutterstock.com/g/foxpictures">FoxPictures</a>/Shutterstock.com</figcaption></figure>



<h2 id="h-methods-to-mitigate-space-junk">Methods to Mitigate Space Junk</h2>



<p>So what can we do about space junk? We've got a few options. Much like the trash problem we have on Earth, the best route is to reduce the amount of trash we send into space. But we all use cellphones and GPS, so we need to continue sending some things into space. This means we need a plan to deal with the space debris.</p>



<h3 id="h-space-junk-retrieval">Space Junk Retrieval</h3>



<p>Retrieving space junk has never been done before. The idea of space debris retrieval is to send a spacecraft into LEO with the intention of grabbing a large piece of space junk. Once the spacecraft has a hold of the junk, it would plunge into Earth's orbit, where it would burn up as it falls towards Earth. This method could be useful for grabbing the larger pieces of junk, such as old rocket upper stages. However, it is unlikely to make economic sense to perform retrieval for smaller pieces of space trash. One idea is to create a spacecraft that can retrieve multiple items of space junk at a time before diving into Earth's atmosphere.</p>



<p>One challenge with space junk retrieval is that old satellites and pieces of rockets weren't created with the intention of being caught. They don't have easy parts to grab onto, so each retrieval mission may need to be custom-built for the particular piece of space trash.</p>



<figure class="wp-block-image alignnone wp-image-1887859 size-full"><img src="https://www.earth.com/wp-content/uploads/2021/01/shutterstock_628124060.jpg" alt="International space station" class="wp-image-1887859"/><figcaption>A 3-D rendition of the ISS. <a href="https://www.shutterstock.com/g/Sasa+Kadrijevic">Limbitech</a>/Shutterstock.com</figcaption></figure>



<h3 id="h-creating-satellites-with-docking-ports">Creating Satellites With Docking Ports</h3>



<p>Some astrophysicists think that all satellites sent into LEO should have a universal docking port for later retrieval. This could be a magnetic surface that a different spacecraft could easily latch onto for retrieval. These ports would make the collection of dysfunctional satellites much easier.</p>



<h3 id="h-high-powered-lasers">High Powered Lasers</h3>



<p>China is investigating sending up a space station with a <a href="https://phys.org/news/2018-01-china-space-junk-lasers.html" target="_blank" rel="noopener">high powered laser onboard</a>. This laser would shoot space debris with high-energy beams. This energy would alter the orbit of the debris, either moving it into Earth's atmosphere, where it would burn up, or further away from LEO where it isn't as much of a problem.</p>



<h2 id="h-efforts-to-clean-up-space-junk">Efforts to Clean Up Space Junk</h2>



<p>While very few people are working on solving the problem of space junk, a few start-up companies aim to do just that. Unfortunately, there isn't a huge market for retrieving trash from space. Just as it is tough to get rid of trash on Earth, it is even harder to get rid of it in space.</p>



<figure class="wp-block-image"><img src="https://www.earth.com/wp-content/uploads/2021/01/shutterstock_1718232061.jpg" alt="" class="wp-image-1887860"/><figcaption><a href="https://www.shutterstock.com/g/djhayazaa">19 STUDIO</a>/Shutterstock.com</figcaption></figure>



<h3 id="h-clearspace">ClearSpace</h3>



<p><a href="https://clearspace.today/" target="_blank" rel="noopener">ClearSpace</a> is going to launch the <a href="https://spacenews.com/clearspace-contract-signed/" target="_blank" rel="noopener">first-ever mission</a> to retrieve space trash in 2025. This European-based mission aims to retrieve a large upper stage of a European Space Agency Vega rocket. They plan to use a net to capture the rocket stage. Once captured, the spacecraft will drag it into Earth's orbit. This project is slated to cost over <a href="https://clearspace.today/" target="_blank" rel="noopener">120 million Euros,</a> all to capture one piece of junk. And you know what's even crazier? The entire Vega rocket launched cost just <a href="https://www.cnbc.com/2020/06/19/arianespaces-vega-rocket-challenging-spacex-rocket-lab-in-the-small-satellite-market.html" target="_blank" rel="noopener">40 million dollars</a>! That's 1/3 the price of retrieving the piece of trash from the rocket!</p>



<h3 id="h-astroscale">Astroscale</h3>



<p><a href="https://astroscale.com/" target="_blank" rel="noopener">Astroscale,</a> a Japanese company, is the oldest and largest group working to solve the space debris problem. They have all sorts of fun ideas on their website. One of their ideas is to provide a service to private satellite owners. Their service would be a <a href="https://astroscale.com/services/end-of-life-eol/" target="_blank" rel="noopener">small spacecraft that flys near the satellite</a>. During the satellite's lifetime, the buddy spacecraft could dock onto the satellite to adjust its flight path. Once the satellite dies, the buddy would dock onto it and pull it into Earth's atmosphere. If all satellites had such a system, any satellite launched would have a plan to get out of LEO, reducing the space debris problem.</p>



<figure class="wp-block-image"><img src="https://www.earth.com/wp-content/uploads/2021/01/shutterstock_1493390582.jpg" alt="" class="wp-image-1887861"/><figcaption><a href="https://www.shutterstock.com/g/DimaZel">Dima Zel</a>/Shutterstock.com</figcaption></figure>



<h2 id="h-let-s-be-proactive-on-space-debris-or-maybe-not">Let's Be Proactive on Space Debris! Or Maybe Not?</h2>



<p>As with most problems, it seems that being proactive on the issue of space junk would be a smart idea. As humans launch more and more rockets into space, the problem will only get worse if we do nothing about it. <strong>If we are serious about space exploration, we must tackle the space debris problem sooner rather than later.</strong></p>



<p>On the other hand, maybe cleaning up the space debris isn't worth the cost. If we don't plan to have humans in space, perhaps accepting the chances of a satellite collision is more economic than actively removing junk from space.</p>



<p>Either way, this issue will be intriguing to follow in the decades to come.</p>



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What Happens to All the Space Junk?

Just as humans have polluted planet Earth's oceans, lands, and...

Common names can often be misleading. The electric eel isn't actually an eel. The red panda is more closely related to a raccoon than a panda. Surprisingly, the killer whale is actually a porpoise, meaning it is closer to a dolphin than a true whale. The so-called flying squirrel is an especially misleading name. <strong>While they can move accurately through the air, they don't exactly fly.</strong>
<h2>What Does It Take to Fly?</h2>
All flying things have an airfoil in some way or another. A wing on an airplane is a textbook example of an airfoil. The special shape of these airfoils, whether it be the wings on a plane, the blades on a helicopter, or the wings of a bird, all produce a force called lift. This lift is caused by the airfoil creating a low-pressure system above the wing and relatively higher pressure below it. The object is pushed up towards the low-pressure area. Don't worry, understanding the physics here isn't that important.

[caption id="attachment_1886126" align="alignnone" width="2560"]<img class="wp-image-1886126 size-full" src="https://www.earth.com/wp-content/uploads/2020/11/shutterstock_1613469793-scaled.jpg" alt="flying squirrel" width="2560" height="1399" /> A basic diagram of the profile of an airfoil.[/caption]
<h3>Flying Requires Thrust</h3>
In order to actually fly, flyers need another force in addition to lift. If you dropped an airplane from 30,000 feet in the air, it would immediately begin falling if the propellers weren't spinning. These propellers produce that other necessary force, which is thrust. Instead of spinning propellers, animals produce thrust by flapping their wings. The combined forces of thrust and lift allow birds, insects, and bats to fly.
<h3>Wing Shape Is Crucial For Flight Style</h3>
However, not all wing shapes are created equal. To be efficient, a wing needs a high aspect ratio. An aspect ratio is the length of the wing from side to side compared to the width of the wing from front to back. <a href="https://www.treehugger.com/albatross-facts-5073421" target="_blank" rel="noopener noreferrer">Albatross</a>, the birds with the longest wings, have one of the highest aspect ratios of all creatures since their wings are incredibly wide from side to side and quite narrow from front to back. The narrow wing tip helps flyers like the albatross use less energy when flapping.

[caption id="attachment_1886127" align="alignnone" width="1000"]<img class="wp-image-1886127 size-full" src="https://www.earth.com/wp-content/uploads/2020/11/shutterstock_1674501214.jpg" alt="Albatross flying" width="1000" height="667" /> This albatross has long, narrow wings, which gives it a high aspect ratio.[/caption]

Chickens, in contrast, have relatively short wings from side to side, but relatively long wings from front to back. This wing shape allows the chicken to produce a lot of thrust when flapping its wings, meaning chickens can quickly burst away from danger. But their wing shape comes at a cost; moving chunky chicken wings takes a lot of energy. This is partly why chickens, turkeys, and other game birds don't fly far distances.

But what about flying squirrels? Flying squirrel wings are much more like that of chickens but more exaggerated. Their wings are short from side to side and long from front to back. This shape means that flying squirrels have a very low aspect ratio, unlike that of birds or airplanes. <strong>This difference in 'wing' shape illustrates the flying squirrel's true method of movement, which is gliding.</strong>

[caption id="attachment_1886128" align="alignnone" width="1000"]<img class="wp-image-1886128 size-full" src="https://www.earth.com/wp-content/uploads/2020/11/shutterstock_253458589.jpg" alt="flying squirrel wings" width="1000" height="750" /> The flying squirrel wings are long from front to back and short from side to side, giving them a low aspect ratio.[/caption]
<h2>An Overview of Gliding</h2>
Imagine trying to flap a large, square piece of cardboard against the air. The cardboard will encounter a substantial amount of air resistance. This air resistance pushes back against the cardboard. If you were a bird with a wing-shaped like this cardboard (which is more like the chicken), you would experience difficulty flapping fast enough to actually fly. If you do the same thing with a long, narrow hockey stick (like the albatross), for example, you will feel minimal air resistance pushing back against the stick. Most bird's wings are more like the hockey stick, whereas the flying squirrel's 'wing' is like the cardboard in our example.

While it is challenging to flap the cardboard, the force of the air pushing up on the cardboard is exactly what the flying squirrels take advantage of. When they jump from high up in a tree, the flying squirrel extends its arms and legs, which have a wing-like membrane between them. This membrane catches air resistance, which slows the squirrel's fall to make it a glide. The squirrels never actually flap. Instead, they adjust their 'wings' to catch different amounts of air resistance on each side of their body. This way, they can move left or right, or even make a complete 180-degree turn.

Since the squirrels don't add thrust to their lift, they aren't technically flying squirrels. They are gliding squirrels. As a result, <strong>they never end up higher above the ground when they land from gliding as opposed to when they took off</strong>. They always lose some altitude. This also means that flying squirrels have a limit on how far they can 'fly.' When they jump from higher up, they can glide further. If they jump from ten feet above the ground, they won't get very far.

[caption id="attachment_1886129" align="alignnone" width="1000"]<img class="wp-image-1886129 size-full" src="https://www.earth.com/wp-content/uploads/2020/11/shutterstock_203464186.jpg" alt="flying squirrels" width="1000" height="667" /> Aren't flying squirrels cute?[/caption]
<h2>Flying Squirrels Are Still Exciting!</h2>
Even without flapping, <strong>flying squirrels can glide hundreds of linear feet through the forest in a single glide</strong>. Gliding is an energy-efficient method of traveling through an open forest. Instead of running up and down every tree they want to forage on, flying squirrels can simply leap from one to another. Imagine you were at a sports stadium. If you could, it would be much easier to glide from one side of the bleachers to the other than to run down the bleachers, across the field, and up the other side of the bleachers. Since flying squirrels glide like this hundreds of times in a given night, the energy savings add up. It is also much quicker to glide between trees. so flying squirrels save precious foraging time by gliding rather than running.

<strong>There are about fifty species of flying squirrels in the world</strong>. All but five live in the temperate and tropical regions of Asia. Three live in North America, and the other two live in northern Eurasia. The high density of gliding species in southern Asia is probably a result of the forest structure. Humans are even <a href="https://www.earth.com/news/newest-species-flying-squirrel/" target="_blank" rel="noopener noreferrer">discovering and rediscovering</a> new species of flying squirrels today!

Forests there have tall trees with open canopies. The higher up their take-off, the further flying squirrels can glide. Therefore, gliding is more evolutionary advantageous in habitats like the tall rainforest canopies of Asia than the open savannahs of Africa.

[caption id="attachment_1886130" align="alignnone" width="1000"]<img class="wp-image-1886130 size-full" src="https://www.earth.com/wp-content/uploads/2020/11/shutterstock_1378010477.jpg" alt="flying lemur" width="1000" height="667" /> A flying lemur clings to a tree.[/caption]
<h2>Are There Other Gliders</h2>
Unlike flying, which has only evolved in insects, bats, birds, and <a href="https://www.earth.com/news/pterosaur-species-largest-flying-animals/" target="_blank" rel="noopener noreferrer">dinosaurs</a>, gliding is widespread in the animal kingdom. It has evolved time and time again, proving the evolutionary advantage of gliding for all sorts of species.
<h3>Mammals</h3>
Along with the fifty species of flying squirrels, multiple groups of mammals can glide. First are the colugos, also known as <a href="https://www.youtube.com/watch?v=SIgv8Qw--kk" target="_blank" rel="noopener noreferrer">flying lemurs</a>. The two species of colugos are most closely related to primates. They are larger than flying squirrels and have more advanced gliding wings.

There are also scaly-tailed squirrels. Unrelated to flying squirrels, eleven species of these animals soar through the forests of central Africa. Lastly, there are the 11 species of gliding possums of Australia and New Guinea. One of these species, the yellow-bellied glider, can glide <a href="http://animalia.bio/yellow-bellied-glider" target="_blank" rel="noopener noreferrer">nearly 400 feet</a>.

[caption id="attachment_1886131" align="alignnone" width="1000"]<img class="wp-image-1886131 size-full" src="https://www.earth.com/wp-content/uploads/2020/11/shutterstock_362165975.jpg" alt="flying frog" width="1000" height="1000" /> A flying frog shows off its webbed feet.[/caption]
<h3>Reptiles</h3>
Reptiles and amphibians have also figured out how to glide. This small <a href="https://www.youtube.com/watch?v=_25rGVEHfSE" target="_blank" rel="noopener noreferrer">flying lizard </a>can glide nearly 200 feet and is also native to Southeast Asia. In fact, there are dozens of species of gliding lizards! A group of frogs that has large, webbed feet can also glide, using their webbed feet to catch air.

<a href="https://www.upi.com/Odd_News/2020/06/30/Researchers-Asian-flying-snakes-wriggle-their-bodies-for-stability/5151593545122/" target="_blank" rel="noopener noreferrer">Even snakes</a> have figured out how to glide! Unlike any other known glider, these snakes' ability to slither through the air actually increases the distance they can glide.
<h3>Insects</h3>
Gliding is actually common in the <a href="https://www.youtube.com/watch?v=JrS0igctMi0" target="_blank" rel="noopener noreferrer">spider world</a> as well. Spiders create long strands of web, which catch air and help them glide long distances. This behavior is called <a href="https://www.earth.com/news/flying-spiders-assess-weather-conditions/" target="_blank" rel="noopener noreferrer">ballooning</a>. Ballooning is probably how spiders colonized isolated islands like Hawaii and New Zealand. If you pay attention, you will likely see stands of silk floating through the air while you are outside. These are probably airborne spiders floating to new homes.

[caption id="attachment_1886132" align="alignnone" width="1000"]<img class="wp-image-1886132 size-full" src="https://www.earth.com/wp-content/uploads/2020/11/shutterstock_412198594.jpg" alt="flying fish" width="1000" height="649" /> A flying fish glides over the ocean.[/caption]
<h3>Fish</h3>
Lastly, over fifty species of fish can also glide through the air. They propel themselves out of water and use modified fins to <a href="https://www.youtube.com/watch?v=bk7McNUjWgw" target="_blank" rel="noopener noreferrer">catch the air</a> and glide above the ocean. Gliding has independently evolved in insects, mammals, reptiles, fish, amphibians, and even mollusks (in the case of the flying squid). As you may have noticed, almost all of these animals' names include the word flying. But really, like the 'flying' squirrel, they are all simply gliders.
<h2>Our Backyard Squirrels Glide, Too</h2>
While they don't truly fly, flying squirrels are nonetheless fascinating forest creatures. They are not too different from our common backyard squirrels, which are also impressive jumpers in their own right. In fact, regular squirrels use their bodies similarly to flying squirrels to jump further and land safer. If you've got 20 more minutes to dedicate to your squirrel knowledge, <a href="https://www.youtube.com/watch?v=hFZFjoX2cGg" target="_blank" rel="noopener noreferrer">this video</a> is certainly a comic, valuable watch. The engineer describes how our backyard squirrels maneuver so well in the air, much like their gliding cousins. Next time you see a squirrel jump, pay attention to the calculated way in which it moves its body to fly through the air!

Check us out on <a href="https://www.earth.com/earthsnap/">EarthSnap</a>, a free app brought to you by Eric Ralls and Earth.com.

Do Flying Squirrels Exist? Not Exactly.

Common names can often be misleading. The electric eel isn't...

<span style="font-weight: 400;">Humans have pondered the beginning of the universe since our species evolved. Generations of people have looked towards the sky as a source of amazement, religion, and wonder. Thankfully, <a href="https://www.earth.com/earthpedia-articles/cosmology/" target="_blank" rel="noopener noreferrer">over the last several centuries</a>, scientists from around the world have begun to piece together empirical data to support a variety of hypotheses about how all of life as we know it began. Today, let’s take a closer look at an age-old question: what are the theories of the universe?</span>

<span style="font-weight: 400;">
</span>
<img class="alignnone wp-image-1882781 size-large" src="https://www.earth.com/wp-content/uploads/2020/07/solar-system-11188_1280-1024x640.jpg" alt="big bang explosion, one theory of the universe" width="1024" height="640" />
<h2>The Big Bang Theory</h2>
<span style="font-weight: 400;">The most robust, well-supported theory as to the origins of the universe is the Big Bang Theory. A Belgian priest, </span><a href="https://www.luc.edu/catholicstudies/newsevents/featuredintellectual/archive/name,306772,en.shtml" target="_blank" rel="noopener noreferrer"><span style="font-weight: 400;">Georges Lemaître</span></a><span style="font-weight: 400;">, first suggested the idea of big bang theory in the 1920s. <strong>Since then, Einstein’s theory of relativity and modern science has lent credibility to this developing theory.</strong></span>
<h3>Big Bang Assumptions</h3>
<span style="font-weight: 400;">Before we can get into specifics, let’s understand a few basic assumptions concerning the Big Bang Theory. Each of the following points is assumed to be true in the universe, and this notion is part of the foundation upon which the Big Bang rests. </span>
<ol>
 	<li style="font-weight: 400;"><b>The universe </b><a href="https://blogs.scientificamerican.com/guest-blog/are-the-constants-of-physics-constant/" target="_blank" rel="noopener noreferrer"><b>is constant</b></a><b>.</b><span style="font-weight: 400;"> This one is first for a reason; it’s important. Our modeling and understanding of the world hinge on the idea that physical properties are the same everywhere. For example, we assume <a href="https://www.earth.com/video/100-years-since-einsteins-theory-of-gravity/" target="_blank" rel="noopener noreferrer">gravity</a>, electricity, magnetism, and light all behave the same way, even in far off places in the galaxy and universe. </span></li>
 	<li style="font-weight: 400;"><b>The universe </b><a href="http://www.earth.com/earthpedia-articles/nettle-tea-benefits-and-how-to-brew-it/" target="_blank" rel="noopener noreferrer"><b>is homogenous</b></a><b>.</b><span style="font-weight: 400;"> Secondly, we assume that the universe is roughly the same in all directions. You can think of these like shovelfuls of dirt. Some scoops might have big rocks, some might have worms, and some may have more clay than others. But, in the long term, every 100 shovelfuls will be roughly the same in composition.</span></li>
 	<li style="font-weight: 400;"><b>The universe is not centered around us.</b><span style="font-weight: 400;"> Physicists refer to this notion as the “</span><a href="https://www.jstor.org/stable/25171345?seq=1" target="_blank" rel="noopener noreferrer"><span style="font-weight: 400;">privileged location</span></a><span style="font-weight: 400;">.” This means that earth is somewhere in the universe, but we really have no idea where it is in relation to the “edge” (more on that later).</span></li>
 	<li style="font-weight: 400;"><b>The universe has a beginning.</b><span style="font-weight: 400;"> All matter and energy that has ever been and that will ever be were created during the Big Bang. No new material or energy has been created since then.</span></li>
</ol>
<h3>Basics of the Big Bang</h3>
<span style="font-weight: 400;">The Big Bang is the leading theory as to the origins of the universe as we know it. It describes the mechanism by which everything we know started as a small singularity that ballooned into the earth, solar system, galaxy, and universe. The easiest way to understand this theory is through a timeline, so let’s dig in.</span>
<ol>
 	<li style="font-weight: 400;"><b>1 second.</b><span style="font-weight: 400;"> During the first second, the temperature around the big bang was about </span><a href="https://science.nasa.gov/astrophysics/focus-areas/what-powered-the-big-bang/" target="_blank" rel="noopener noreferrer"><span style="font-weight: 400;">5.5 billion degrees</span></a><span style="font-weight: 400;"> celsius (10 billion Fahrenheit). There would have been nothing to see at this point, though. According to </span><a href="https://science.nasa.gov/astrophysics/focus-areas/what-powered-the-big-bang" target="_blank" rel="noopener noreferrer"><span style="font-weight: 400;">NASA</span></a><span style="font-weight: 400;">, “the free electrons would have caused light (photons) to scatter the way sunlight scatters from the water droplets in clouds.”</span></li>
 	<li style="font-weight: 400;"><b>3 seconds.</b><span style="font-weight: 400;"> The initial explosion contained all the necessary subatomic particles for atoms and molecules: neutrons, protons, and electrons. The first basic elements form at this point: hydrogen, helium, and lithium. </span></li>
 	<li style="font-weight: 400;"><b>380,000 years.</b><span style="font-weight: 400;"> For the first time, light emerges into the universe. This radiation (light) is referred to as the cosmic microwave background. First predicted to exist in 1948 by </span><a href="https://cosmology.carnegiescience.edu/timeline/1948" target="_blank" rel="noopener noreferrer"><span style="font-weight: 400;">Ralph Alpher</span></a><span style="font-weight: 400;">, it is a signature mark of the Big Bang. This background of microwaves can still be observed today, and it used to estimate the age of the universe. </span></li>
 	<li style="font-weight: 400;"><b>300 million years.</b><span style="font-weight: 400;"> We’re jumping forward a bit here. As the initial burst of atoms and gas expands, gravity starts to become a relevant factor. Pockets of different densities of gas </span><a href="https://www.scientificamerican.com/article/how-is-a-star-born/#:~:text=A%20star%20is%20born%20when,until%20the%20fusion%20reactions%20begin." target="_blank" rel="noopener noreferrer"><span style="font-weight: 400;">give birth to stars</span></a><span style="font-weight: 400;"> and collections of stars start to form galaxies. </span></li>
 	<li style="font-weight: 400;"><b>~9 billion years.</b><span style="font-weight: 400;"> Our sun forms. <strong>The universe is roughly 14 billion years old, and our sun is approximately 4.6 billion years old. </strong></span></li>
</ol>
<img class="alignnone size-large wp-image-1882782" src="https://www.earth.com/wp-content/uploads/2020/07/earth-1617121_1920-1024x575.jpg" alt="earth from space" width="1024" height="575" />
<h2>Steady State Universe</h2>
<span style="font-weight: 400;">The steady state universe hypothesis breaks one of the key Big Bang Theory assumptions. The </span><a href="http://abyss.uoregon.edu/~js/glossary/steady_state.html" target="_blank" rel="noopener noreferrer"><span style="font-weight: 400;">steady state hypothesis</span></a><span style="font-weight: 400;"> states that matter and energy are being created continuously, steadily. First theorized in the 1920s by Sir James Jeans, the theory imagines a universe without a real beginning or end. </span>

<span style="font-weight: 400;">In the steady state view, the universe has always been expanding and creating matter, and it will continue to do so. Although the theory has been revised and updated throughout the middle of the 20th century, an overwhelming amount of contradictory evidence supports the notion that <strong>the steady state hypothesis is largely false</strong>. </span>

<img class="alignnone wp-image-1882783 size-large" src="https://www.earth.com/wp-content/uploads/2020/07/universe-2742113_1280-1024x482.jpg" alt="cosmos" width="1024" height="482" />
<h2>Level II Multiverse</h2>
<span style="font-weight: 400;">The multiverse concept </span><a href="https://space.mit.edu/home/tegmark/PDF/multiverse_sciam.pdf" target="_blank" rel="noopener noreferrer"><span style="font-weight: 400;">is complicated</span></a><span style="font-weight: 400;">. And, that may still be an understatement. One of the driving factors leading to the development of this theory is the seemingly perfect nature of physics in our universe. Light, gravity, physics… they all seem to work together perfectly to allow life to exist in our universe. This can be viewed as a major coincidence or an inevitability given a large number of trials. </span>

<span style="font-weight: 400;">The <a href="https://www.earth.com/news/life-possible-other-universes/" target="_blank" rel="noopener noreferrer">multiverse</a> concept postulates that multiple universes exist, simultaneously, and they each have different physical constants. For example, maybe a universe 2.0 (or 3.0 or 18.0 or 821.0) exists along with ours where light travels at a different speed. Changing this speed changes an exceptionally large number of other universal constants, and thus, everything we know about our universe.</span>
<h2>Correct Hypothesis?</h2>
<span style="font-weight: 400;">So, where does that leave us? What is the “correct” theory for the origin of the universe? By a large margin, the Big Bang is the most well-supported, evidence-based theory. That being said, new technology and new instruments allow us to gather different data every decade, so we will have to see what the future holds! </span>

<span style="font-weight: 400;">What other theories of the universe have you heard of? How do you think this all got here?</span>

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What Are the Theories of the Universe?

Humans have pondered the beginning of the universe since our...

<div itemprop="video" itemscope itemtype="http://schema.org/VideoObject"><div id="58e3ebce955a315103d39bd1" class="vdb_player vdb_58e3ebce955a315103d39bd158d96b98cd4fed198a0d2a49"  >    <script type="text/javascript" src="https://delivery.vidible.tv/jsonp/pid=58e3ebce955a315103d39bd1/vid=5cb5d7bde98ab5792e009cde/58d96b98cd4fed198a0d2a49.js?"></script></div>    <meta itemprop="name"content="What are the Physics of Global Warming?" />    <meta itemprop="duration" content="T2M48S" />    <meta itemprop="thumbnailUrl" content="https://img.vidible.tv/prod/2019-04/16/5cb5d7bde98ab5792e009cde/5cb5d7f69d15d700019e8e70_1280x720_FES_v1.jpg" />    <meta itemprop="embedUrl" content="https://delivery.vidible.tv/htmlembed/pid=58e3ebce955a315103d39bd1/58d96b98cd4fed198a0d2a49.html?vid=5cb5d7bde98ab5792e009cde" />    <meta itemprop="uploadDate" content="2019-04-16T13:32:00Z" />    <meta itemprop="expires" content="" />    <meta itemprop="description" content="" />    <meta itemprop="height" content="720" />    <meta itemprop="width" content="1,280" /></div>

&nbsp;

The observed global warming on Earth is a manifestation of the Second Law of Thermodynamics. The Earth operates like any heat engine. Input heat from solar radiation and exhaust heat, in this case, terrestrial radiation, largely determine the operating temperature or "global surface temperature". Over geological periods this heat exchange reaches equilibrium and the temperature is stable. If the input heat increases or the exhaust heat decreases the temperature rises and vice versa. Natural processes over geologic time have changed the input and affected both output heat and outside temperature.

In the present era, the quantity of exhaust heat is being rapidly restricted by the greenhouse effect; consequently, the earth's temperature must rise to reach equilibrium. How much higher it must rise depends on human activity, many pose.

The input heat, the solar energy received, is a function of solar activity and oscillations in characteristics of the Earth’s orbit.

The quantity of exhaust heat, terrestrial radiation, is largely a function of the presence of certain gases in the atmosphere that absorb outgoing infrared radiation. This is known as the greenhouse effect. The greenhouse effect is due to the differential absorption of certain wavelengths of solar as compared to terrestrial radiation.

The solar energy reaching the surface of the Earth is concentrated in short wavelengths, which can easily penetrate the greenhouse gases, such as Carbon Dioxide and Methane. The Earth, however, is cooler than the sun and it radiates its heat in the form of energy in the far infrared range. These longer wavelengths are partially absorbed by the greenhouse gases and some of the solar heat is returned to planet Earth.

At a certain temperature, these processes are in equilibrium and the surface temperature of the Earth is stable. However, if more greenhouse gases are put in the atmosphere the amount of trapped terrestrial radiation increases, leading to an increase in global temperature.

Currently the heating effect of extra greenhouse gases, since the start of the industrial revolution, from the mid 1700s to the mid 1800s, is equal to about one watt per square meter.

That means the recent period has recorded parallel increases in concentration of carbon dioxide and the average global temperature. As more greenhouse gases are put into the atmosphere the temperature will increase further. There are certain effects of a warmer Earth which could accelerate the process, even if no more greenhouse gases are put into the atmosphere.

We respectfully credit <a href="https://www.ck12.org" target="_blank" rel="noopener noreferrer">CK12.org</a>. Those who provide Open Source, educational information need your support!

&nbsp;

What Are the Physics of Global Warming?

&nbsp; The observed global warming on Earth is a manifestation...

The universe is vast and mostly empty. Imagine traveling from your house to the nearest galaxy. Even if you moved at lightspeed (the speed limit of the universe), this trip <a href="https://www.universetoday.com/21914/the-closest-galaxy-to-the-milky-way/" target="_blank" rel="noopener noreferrer">would take 25,000 years</a>. For most of this time, you would be speeding through what appears to be an empty void. In this space, there is nothing for light to reflect off or be absorbed by. However, even in this empty void, <b>SOMETHING </b>exists. What this something is is still unknown to science. Mysterious, "dark energy" is spread throughout this void.

&nbsp;
<h2><strong>Empty Space and The Expansion of the Universe</strong></h2>
[caption id="attachment_1873557" align="alignnone" width="3000"]<img class="size-full wp-image-1873557" src="https://www.earth.com/wp-content/uploads/2019/06/CMB_Timeline300_no_WMAP.jpg" alt="A timeline of the expansion of the universe from the big bang to the present." width="3000" height="1980" /> The history of the universe shows accelerating expansion.[/caption]

&nbsp;

Physicists deduced the existences of this elusive dark energy stuff from the laws of physics and our observations of the universe. Decades of research and the development of advanced technology have allowed us to get a better picture of our universe. However, rather than neatly answering our questions this research has created even more questions. This is often the way science works.

Theoretical models show that there is <a href="https://science.nasa.gov/astrophysics/focus-areas/what-is-dark-energy" target="_blank" rel="noopener noreferrer">far too little visible matter</a> in the universe. The math simply doesn’t work! Therefore, physicists believe there are large amounts of matter that do not behave like normal matter. This implies the existence of an entirely new type of particle, called "dark matter." What this dark matter is, and how it behaves is unknown.

In addition, the universe is expanding. As this happens, the expansion accelerates. Why this happens, however, is unknown. This expansion is not explained by the known laws of physics. Instead, it seems to be a property of empty space or something that fills space that appears empty. Astrophysicists call this force dark energy.

&nbsp;
<h2><strong>Visible Matter Makes Up Less Than 5% of the Universe</strong></h2>
These two observations imply that we cannot observe a large part of what makes up the universe. Most of this undetected energy/matter is dark energy, which makes up ~74% of the universe. Dark matter makes up another 22% of the universe.

The matter that we know and see <a href="http://hubblesite.org/hubble_discoveries/dark_energy/de-what_is_dark_energy.php" target="_blank" rel="noopener noreferrer">makes up only 4% of the universe</a>. This is called baryonic matter, named for the subatomic particles (baryons) everything we see is made of. This 4% includes all the suns, planets, nebulae and black holes of the universe. This means 96% of the universe is still a complete mystery.

&nbsp;
<h2><strong>The Accelerating, Expanding Universe</strong></h2>
[caption id="attachment_1873556" align="alignnone" width="1600"]<img class="size-full wp-image-1873556" src="https://www.earth.com/wp-content/uploads/2019/06/Hubble_ultra_deep_field.jpg" alt="The hubble ultra deep field image showing countless galaxies in the depths of seemingly empty space." width="1600" height="1600" /> The Hubble Deep Field Image shows a tiny patch of the night sky that has few visible stars. However, it is full of galaxies.[/caption]

&nbsp;

Since the late 20th century, astrophysicists have known that the universe is expanding. Observations by telescopes on earth have shown that distant galaxies are moving away from the center of the universe.

The expansion of the universe was assumed to be slowing down due to the gravity of all the matter in the universe. However, new evidence disproved this belief.

The launch of the Hubble Space Telescope (HST) <a href="https://www.earth.com/earthpedia-articles/large-scale-structure-of-the-cosmos/" target="_blank" rel="noopener noreferrer">enabled more accurate observations</a> of the universe on a large scale. It also allowed physicists to look back in time. Because light travels at a set maximum speed, it takes time to cross the universe. Light from the earliest stages of the universe is still making its way back to earth. This allows astronomers to look back in time to understand how the universe is changing.

The HST made observations of the <a href="http://astronomy.swin.edu.au/cosmos/D/Dark+Energy" target="_blank" rel="noopener noreferrer">type Ia supernovae</a>. As these supernovae move away from us, the light we see changes. This is similar to the Doppler effect you experience when an ambulance drives by with its sirens on. With light, this same effect causes the light to ‘redshift.’ By measuring these changes astrophysicists discovered the expansion of the universe is accelerating.

The acceleration of expansion challenges Einstein's theory of gravity. For this phenomenon to make sense, there must be an undiscovered form of energy fueling this acceleration. This energy is evenly distributed across the universe, filling the void. This unknown force has been dubbed “dark energy.” Though we know it exists, we still have never directly measured it.

&nbsp;
<h2><strong>Space Creates Space</strong></h2>
The expansion of the universe appears to be fueled by empty space itself. The areas of the universe that already have matter are not expanding. This means the earth and sun are not moving away from each other. Instead, this expansion occurs in the parts of the universe that are already empty.

This dark energy seems to <a href="https://earthsky.org/space/what-is-dark-energy" target="_blank" rel="noopener noreferrer">interact with gravity in reverse</a>. Rather than pulling things together, dark energy seems to push objects apart. Rather than pulling objects faster, the close they are, dark energy pushes objects faster when they are far apart.

&nbsp;
<h2><strong>Dark Matter vs. Dark Energy</strong></h2>
Though dark energy and dark matter are both mysterious properties of our universe, they are different from each other. These two concepts exist to explain different gaps in our knowledge. They are both “dark” because we cannot directly observe them. However, according to <a href="https://www.earth.com/news/dark-matter-energy/" target="_blank" rel="noopener noreferrer">some theories</a> dark energy and dark matter may be the same. As Einstein demonstrated e=mc2 for normal matter and energy, the same may be true for dark matter and energy.

&nbsp;
<h2><strong>Possible Explanations of Dark Energy</strong></h2>
<h3>1. Einstein’s Forgotten Cosmological Constant</h3>
<img class="size-full wp-image-1873558 alignnone" src="https://www.earth.com/wp-content/uploads/2019/06/albert-einstein-1165151-1.jpg" alt="Albert Einstein in front of a chalk board" width="1800" height="2364" />

&nbsp;

Part of Einstein’s original theory of relativity involved a concept called the <a href="https://www.nationalgeographic.com/science/space/dark-matter/" target="_blank" rel="noopener noreferrer">Cosmological Constant</a>. This was an idea that Einstein later rejected, calling it his “biggest blunder.” However, the theory seems to align with our understanding of dark energy. The cosmological constant was a repulsive force, counteracting gravity and preventing the universe from collapsing in on itself.

&nbsp;
<h3><strong>2. Virtual Particles</strong></h3>
Another theory is that empty space is <a href="https://science.nasa.gov/astrophysics/focus-areas/what-is-dark-energy" target="_blank" rel="noopener noreferrer">filled with “virtual” particles</a>. These particles come into existence and are immediately canceled out. These particles could produce the force of dark energy. However, calculations of the energy this would produce are over 100,000 times different from observations.

&nbsp;
<h3><strong>3. The Quintessence Energy Field</strong></h3>
Another possibility is that there is a new, unknown kind of energy in the universe. This energy would represent a new field, different from electromagnetism, gravity and other known forces. This force is referred to as <a href="https://physicsworld.com/a/quintessence/" target="_blank" rel="noopener noreferrer">quintessence</a>. This word comes from an ancient Greek concept of a fifth element that is a perfect substance.

&nbsp;
<h3><strong>Or Everything We Know is Wrong</strong></h3>
The other possibility is that <a href="https://earthsky.org/space/what-is-dark-energy" target="_blank" rel="noopener noreferrer">Einstein’s theory of relativity is wrong</a>. Though Einstein’s theory is the only working explanation for the behavior of mass and energy in our solar system, there are some places where it falls apart. The accelerating expansion of the universe is unexplained by the theory of relativity.

In addition, the behavior of <a href="https://www.earth.com/image/10-must-see-science-documentaries-streaming-now-evrything-and-nothing-amazon-prime/">tiny particles</a>, called quantum physics, is completely different from the behavior of large objects. Quantum physics has not been reconciled with Einstein’s theory of general relativity. The answers to what dark energy is may lie in the answer to this equally difficult problem.

&nbsp;

Dark Energy is a mysterious thing. The fact that it makes up the majority of energy in our universe poses big questions. It challenges much of what we thought we knew about the universe. As we learn more about the universe we learn more about just how little we understand. However, this shouldn’t come as disappointing news. Scientists are continuing to study these phenomena and create new efforts to expand human knowledge. This includes mapping the energy of the known universe to complete the <a href="https://www.darkenergysurvey.org/" target="_blank" rel="noopener noreferrer">Dark Energy Survey</a>. These efforts aim to answer these questions. However, the new questions they reveal may be even more strange.

&nbsp;

Watch this video for a summary of what we know about dark energy and dark matter.

[embed]https://www.youtube.com/watch?v=QAa2O_8wBUQ[/embed]

&nbsp;

What Is Dark Energy?

The universe is vast and mostly empty. Imagine traveling from...

Though we rarely think about them, we rely on satellites for much of our daily lives. They enable global communication, GPS and weather reports. Satellites also help <a href="https://www.earth.com/image/nasa-satellite-measures-deforestation/" target="_blank" rel="noopener">measure environmental destruction</a>, <a href="https://www.earth.com/image/new-weather-satellite-detail/" target="_blank" rel="noopener">track weather</a>, <a href="https://www.earth.com/news/satellites-track-sea-level/" target="_blank" rel="noopener">sea levels</a>, and even <a href="https://www.earth.com/news/map-living-conditions-global-poverty/" target="_blank" rel="noopener">global economics</a>. These satellites face a huge problem - the exponentially growing amount of space junk sharing Low Earth Orbit (LEO).

Satellites don’t last forever. Eventually, they stop working. However, when this happens they do not magically disappear or fall back to earth. These objects remain in their orbit, moving at incredible speeds.

In 1978, NASA astrophysicist <a href="http://iaass.space-safety.org/awards/jerome-lederer-space-safety-pioneer-award/space-safety-pioneer-award-hall-of-fame/kessler-biography/" target="_blank" rel="noopener">Donald J. Kessler</a> made a startling prediction. The growing debris in LEO would eventually reach a tipping point. When this happened, it would start a chain reaction of collisions. Each collision creating more debris, leading to more collisions. <strong>This domino effect is called the Kessler Syndrome.</strong>

If we reach this point, the consequences will be disastrous. The resulting debris field would destroy essential satellites. Pieces of space junk would shred the International Space Station to bits. The cascading debris would make LEO too cluttered for new satellites. This would fundamentally change the way humans use space. Many modern conveniences we take for granted would disappear.

&nbsp;

<img class="alignnone wp-image-1872177 size-full" src="https://www.earth.com/wp-content/uploads/2019/05/space-junk-11644_640.jpg" alt="A map of spacejunk orbiting earth." width="640" height="512" />

&nbsp;
<h2><strong>What Makes Space Junk So Dangerous?</strong></h2>
Compared to the amount of overall waste produced by humanity, space junk may seem pretty minor. It is <a href="http://stuffin.space/" target="_blank" rel="noopener">floating in the void of space</a>. It seems too far away to hurt any of us. Out of sight, out of mind.

The reality is that this “trash” is more like thousands of missiles. <strong>In orbit, space debris generally moves at <a href="https://www.nasa.gov/news/debris_faq.html" target="_blank" rel="noopener">7-8 kilometers per second</a>, over 25,000 kilometers per hour </strong>(15,000 miles per hour.) Collisions are even faster due to the speed of the satellite. At these speeds, a 10-centimeter object would have the force of <a href="https://bigthink.com/paul-ratner/how-the-kessler-syndrome-can-end-all-space-exploration-and-destroy-modern-life" target="_blank" rel="noopener"><b>7 kilograms of TNT</b></a>.

These collisions are still rare, but the amount of space junk is growing. Currently, there are <a href="http://www.au.af.mil/au/awc/awcgate/usspc-fs/space.htm" target="_blank" rel="noopener">8,000 orbiting objects being tracked by the Space Surveillance Network</a>. This is far less than the estimated 22,000 objects larger than 4 inches in orbit. When smaller objects are considered, that number goes into the tens of millions. Each collision has the potential to multiply these objects.

&nbsp;

<img class="alignnone wp-image-1872178 size-large" src="https://www.earth.com/wp-content/uploads/2019/05/international-space-station-67774_1920-1024x680.jpg" alt="The view of earth from the international space station with an astronaut looking out the window." width="1024" height="680" />

&nbsp;
<h2><strong>Do Collisions With Active Satellites Actually Happen?</strong></h2>
There are around 1,000 working satellites in LEO. A number of different countries and private companies own these satellites. Most of these are able to avoid collisions using thrusters. When they detect a threatening object, they make evasive maneuvers. However, with the number of satellites and objects in space, this is not always possible.

In <a href="http://www.spacesafetymagazine.com/space-debris/kessler-syndrome/iridium-33-cosmos-2251-years-later-learned-then/" target="_blank" rel="noopener">2009 the private satellite Iridium 33 collided with the derelict Russian Cosmos 2251</a>. This event revealed the real risks of orbital debris. The collision underscored the realities of the Kessler Syndrome. This led to increased international cooperation to combat the threat.

The largest object in LEO is the international space station (ISS.) This space station houses astronauts continually. A large collision with the ISS would be disastrous. Essential components of the ISS can withstand pieces of space junk up to 1cm. However, about once a year the ISS has to maneuver to avoid a larger collision.

&nbsp;
<h2><strong>How to Prevent the Kessler Syndrome</strong></h2>
<h3><strong>Make Less Trash</strong></h3>
The most important step to prevent the Kessler Syndrome is to create less junk. This means being careful about what we send into space. <a href="https://www.scienceabc.com/nature/universe/what-is-kessler-syndrome-definition-example-effects-solution.html" target="_blank" rel="noopener">Limitations on the number of satellites</a> launched is an obvious step. In addition, organizations must design satellites must with this threat in mind. This means ensuring that they can be safely disposed of when they die. In the US, satellites must reenter the Earth’s atmosphere (where they burn up) or be launched to the “graveyard orbit” well outside of LEO. The UN also has a set of debris mitigation guidelines.

&nbsp;

<img class="alignnone wp-image-1872179 size-large" src="https://www.earth.com/wp-content/uploads/2019/05/dark-2024127_1280-1024x643.png" alt="A meteor of piece of space junk burining up in earth's atmosphere" width="1024" height="643" />

&nbsp;
<h3><strong>Cleanup Efforts</strong></h3>
Even if all new satellites were safely disposed of, collisions could still happen. The daisy chain of the Kessler Syndrome could turn operational satellites into hundreds of new pieces of junk.

Currently, there is no method to remove existing space junk. Some objects will naturally enter the atmosphere in a matter of years. However, those further out will likely <a href="https://www.nasa.gov/news/debris_faq.html" target="_blank" rel="noopener">stay in orbit for centuries</a>.

Research is ongoing into possible cleanup techniques. A “<a href="http://www.spacedaily.com/news/debris-00a.html" target="_blank" rel="noopener">laser broom</a>” is one proposed solutions. This would use lasers to push debris toward reentry. International treaties, cost, and complexity have prevented any significant effort to remove debris.

&nbsp;

The Kessler Syndrome is a very real threat. Pollution is a problem that follows humans everywhere we go, even in space. We can only hope that action to mitigate the dangers of pollution in space will happen quickly enough to prevent disaster.

&nbsp;

What is the Kessler Syndrome?

Though we rarely think about them, we rely on satellites...

<h2></h2>
<h2>The Summer Solstice</h2>
it is derived from the Latin <i>sol</i> (sun) and <i>sistere</i> (to stand still), can be considered the astronomical event to mark the beginning of summer.

For half of the globe, the Solstice day has more sunlight hours than any other day of the year. (excluding Equatorial regions where daylight hours are the same for every season).

On the day of the Summer Solstice (also called Midsummer) in the Northern Hemisphere. The sun reaches its most northerly point in the sky and appears to stand still, just before returning toward its most southerly point, and repeating the cycle. Over the course of a year, the Earth makes one full revolution around the sun.
<h3>Some factors can affect the way light from the sun is distributed over the planet throughout the year like :</h3>
<ul>
 	<li>Earth’s 23.5 degree axial tilt</li>
 	<li>curvature</li>
 	<li>rotation speed of the earth</li>
</ul>
The positioning of the Earth during the Summer Solstice causes the sun’s light to hit the Tropic of Cancer at a 90 degree angle. The angle of the sun’s rays over the Earth at this time gives the North Pole 24 hours of sunlight, while the South Pole remains dark for 24 hours (signifying the Southern Hemisphere’s Winter Solstice).<span class="Apple-converted-space"> </span>

For the Winter Solstice, the sun’s light hits the Tropic of Capricorn at a 90 degree angle. During this time, the South Pole receives 24 hours of sunlight, and the North Pole 24 hours of darkness. At this Solstice, the Southern Hemisphere’s summer is beginning, and the Northern Hemisphere experiences the start of winter. Depending on the shift of the calendar, the Summer Solstice occurs some time between:
<ul>
 	<li>June 20 and June 21 in the Northern Hemisphere</li>
 	<li>December 21 and December 22 in the Southern Hemisphere.</li>
</ul>
Interpretation of the Solstice has varied throughout cultures, but most have recognized it as a sign of fertility, observing holidays, festivals, gatherings, rituals and other celebrations around the time of the Solstice. In Northern Europe, the Summer Solstice is most famously associated with Stonehenge, where the sun has been worshipped for thousands of years.

What is the Summer Solstice?

The Summer Solstice it is derived from the Latin sol...

<strong>Heat lightning</strong> is simply faint flashes of light reflecting outward from distant thunderstorms. The light is actually regular lightning that is seen from over the horizon. These flashes are too far away (10+ miles) to hear the sound that is normally produced by thunderstorms. The reason for the term ‘heat lightning’ is said to be because they often occur on hot summer nights.

Heat lightning being so clearly visible from so far away is a matter of reflection, as well as magnification. Due to light reflecting off of water particles in the moist, humid air, the light is able to spread throughout the upper atmosphere. Over flat terrain, the lightning flashes can be seen up to 100 miles away.

Heat lightning is sometimes an early warning sign of an approaching storm. While lightning normally produces thunder, the sound of thunder rarely travels more than 10 miles. Other factors contributing to the quiet nature of heat lightning are:
<ul>
 	<li>Refraction of the sound over changing densities of air</li>
 	<li>Temperature differences overhead refracting the sound upward</li>
 	<li>Airborne matter muffling the sound of thunder, such as heavy snow during a winter storm. Dust and sand storms are also capable of muffling the sound of thunder</li>
</ul>
Lightning itself is a discharge of electrical energy reaching temperatures of up to 25,000°C — hotter than the surface of the sun. The friction from ice and water particles rubbing together cause positive and negative charges to distribute within storm clouds, producing sparks. What we see during a flash of lightning are streams of plasma that the positive and negatively charged particles can travel through.

Photo Copyright and Credit

What is Heat Lightning?

Heat lightning is simply faint flashes of light reflecting outward...

Condensation is the change of a substance from a gaseous into a liquid form. It is the opposite of evaporation, which is another major steps in the Earth’s water cycle.<span class="Apple-converted-space"> </span>

One example of condensation is the formation of dew. When the air temperature cools to what is called the dew point, water vapor can collect in liquid form and settle on cold surfaces. Water vapor will only condense on a surface when the temperature of the surface is cooler than the water vapor’s temperature.

Water molecules carry a little heat energy and, as they condense, transfer this energy to the atmosphere. When water vapor condenses into liquid water, hydrogen forms and releases latent heat. This increases the sensible heat, and therefore causes the temperature of the air to rise. The sensible heat is removed from the air and the temperature drops when evaporation occurs. This process continues, causing air temperature to rise and fall again as water vapor forms and condenses.

The process of condensation is often utilized to generate large quantities of water for human usage. Many structures — including fog fences, air wells, dew ponds, and distillation equipment — are made solely for the purpose of collecting water formed by condensation. Sometimes these manmade structures and systems can be used to retain soil moisture in more arid, desert areas.

Psychrometry is a science related to condensation. It is the study of thermodynamic properties of moisture in air and the changes of conditions of this moisture. Many times, weather reporters mention relative humidity values and high/low pressure systems — information gathered using psychrometric equipment (such as the sling psychrometer).

Photo Copyright and Credit

What is Condensation?

Condensation is the change of a substance from a gaseous...

Five Ways to Disprove Flat Earth From Your Backyard

Have you ever proved that the Earth isn't flat? While...

<p>That humans have made it to space is a profound, impressive feat that has impacts on our daily lives. We wouldn't be able to see our location on our phones or do anything involving GPS without the <a href="https://www.earth.com/earthpedia-articles/how-many-satellites-in-space-do-we-know-about/" target="_blank" rel="noopener noreferrer">satellites</a> scientists have sent to space. We wouldn't have pictures of Earth from high above or any rocks from the moon. All these accomplishments were possible through science and rockets themselves. While the first rockets appeared as fireworks in China hundreds of years ago, most people think of space ships when they hear the word 'rocket' in the 21st century.</p>



<h2 id="h-rockets-versus-airplanes">Rockets Versus Airplanes</h2>



<p>On the surface, rockets may seem similar to planes. Both fly, both use fuel, and both are intended to move goods around. While their functions may be similar, the mechanisms powering these two flying machines are different. Exploring how planes and rockets are different is a good way to learn what a rocket is.</p>



<h3 id="h-rockets-don-t-have-wings">Rockets Don't Have Wings</h3>



<p>First of all, planes have wings and rockets don't. Wings create lift, which is a force that pushes the plane up in the air against gravity. Air flows over the top of the <a href="https://www.earth.com/earthpedia-articles/do-flying-squirrels-exist-not-exactly/" target="_blank" rel="noopener noreferrer">airfoil</a> faster than underneath the bottom and through some magic of physics, this differential in airspeed creates the force of lift.</p>



<p>But wings are a type of <em>airfoil.&nbsp;</em>The existence of <em>air</em> is why they work. Wings are unnecessary for rockets for a few reasons. First, rockets go straight up through the Earth's atmosphere. Wings produce drag rather than lift if the object is moving straight up. Second, there is no air in space! Therefore, the airfoil wings wouldn't do anything for a rocket in space. Moreover, since rockets must be lightweight, these wings would add unnecessary mass.</p>



<p>Perhaps you're thinking of the space shuttle. Yes, the space shuttle had wings, but these wings were essential for the space shuttle landing back on the Earth. Most of the rocket parts we send to space have don't come back home.</p>



<h3 id="h-rocket-engines-contain-oxygen">Rocket Engines Contain Oxygen</h3>



<p>The biggest difference between rockets and airplanes is how the fuel interacts with oxygen. Both of them rely on thrust from fuel. Thrust is the result of controlled explosions of fuel and oxygen in the engine. These explosions create pressure, which propels the plane or rocket forward.</p>



<p>An easy way to experience thrust yourself is to turn the hose on full blast. Pay attention to how the hose kicks back once the water starts coming out. That force is an example of thrust.</p>



<p>Since our atmosphere is full of oxygen, airplanes can combine atmospheric oxygen with fuel to combust jet fuel and, therefore, create thrust. As with the airfoil mentioned above, the absence of oxygen in space makes the combustion of fuel more difficult.</p>



<p>Instead of using atmospheric oxygen, rockets <a href="https://www.youtube.com/watch?v=OZLXpPeUkhQ" target="_blank" rel="noopener noreferrer">carry their own tanks</a> of oxygen, which are separate from the fuel. The engine of a rocket combines the oxygen and fuel in the rocket to combust and create thrust. By using on-board oxygen, these machines can create thrust in space.</p>



<h2 id="h-parts-of-a-rocket">Parts of a Rocket</h2>



<p>A rocket consists of four main systems; structure, propulsion, payload, and guidance. These four systems work together to guide a the vessel into space.</p>



<h3 id="h-the-rocket-structural-system">The Rocket Structural System</h3>



<p>You can think of the structural system of a rocket as the body. This system holds the payload, guidance, and propulsion systems in place as the rocket does its mission. Similarly, the structural system of a car is the metal frame on which the engine, seats, computer systems, and wheels sit. Unlike a car, the structural system of a rocket is engineered for minimum weight. A more <a href="https://www.nasa.gov/mission_pages/station/expeditions/expedition30/tryanny.html#:~:text=Rockets%20at%2085%25%20propellant%20and,constant%20engineering%20to%20keep%20flying." target="_blank" rel="noopener noreferrer">appropriate analogy</a> would be a soda can, where the can is the structural system and the soda is the propulsion system. A soda can is 94% soda and 6% can, which is very comparable to a rocket.</p>



<figure class="wp-block-image alignnone size-large wp-image-1886835"><img src="https://www.earth.com/wp-content/uploads/2020/12/rocket-1245696_1920-1024x683.jpg" alt="rocket launch" class="wp-image-1886835"/><figcaption>A rocket launches into space. <a href="https://www.shutterstock.com/g/chetannigam94432">Contributor2</a>/Shutterstock.com</figcaption></figure>



<h3 id="h-rocket-propulsion">Rocket Propulsion</h3>



<p>The propulsion system takes up the vast majority of the space in rockets. This is because rockets require massive amounts of fuel and oxygen to produce thrust, which sends the rocket off into space. In the picture of the space shuttle above, the orange cylinder and the two white cylinders are all the propulsion system. In other rockets, the propulsion system takes up even more space. A car, in contrast, is about 4% fuel by weight when the gas tank is full. A rocket, on the other hand, is over <a href="https://www.nasa.gov/mission_pages/station/expeditions/expedition30/tryanny.html#:~:text=Rockets%20at%2085%25%20propellant%20and,constant%20engineering%20to%20keep%20flying." target="_blank" rel="noopener noreferrer">85% fuel by weight</a>!</p>



<h3 id="h-rocket-guidance">Rocket Guidance</h3>



<p>Without a guidance system, rockets wouldn't end up in their desired destinations. Fireworks are examples of rockets without guidance systems. Imagine trying to hit a target thousands (or millions) of miles away with a hand-held firework. That sounds impossible, right? The guidance system on rockets makes adjustments to the flight path ensuring that the rocket reaches its desired destination. The guidance system involves lots of gadgets and computers.</p>



<h3 id="h-rocket-payload">Rocket Payload</h3>



<p>The payload is the whole point of the rocket. This system consists of the functional objects people aim to get into space. Some examples of the payload include astronauts, the space shuttle, satellites, <a href="https://www.inc.com/don-reisinger/elon-musk-sent-his-tesla-roadster-into-space-two-years-ago-heres-where-it-is-now.html" target="_blank" rel="noopener noreferrer">Elon Musk's Tesla</a>, supplies for the International Space Station, space probes, or Mars rovers. Physics demands that the payload be small compared to the propulsion system. A <a href="https://www.nasa.gov/mission_pages/station/expeditions/expedition30/tryanny.html#:~:text=Rockets%20at%2085%25%20propellant%20and,constant%20engineering%20to%20keep%20flying." target="_blank" rel="noopener noreferrer">NASA scientist</a> says "Real payload fractions from real rockets are rather disappointing. The Saturn V payload to Earth orbit was about 4% of its total mass at liftoff. The Space Shuttle was only about 1%."</p>



<figure class="wp-block-image alignnone size-large wp-image-1886836"><img src="https://www.earth.com/wp-content/uploads/2020/12/sputnik-986-1024x839.jpg" alt="sputnik rocket satellite" class="wp-image-1886836"/><figcaption>A Sputnik replica. <a href="https://www.shutterstock.com/g/zaitcev-evgenii">Zenobillis</a>/Shutterstock.com</figcaption></figure>



<h2 id="h-famous-rocket-launches">Famous Rocket Launches</h2>



<p>Below is a shortlist of some of the famous launches in humanity's exploration of space. While hundreds of launches are famous for various reasons, I've focused on just a few that were major milestones in rocketry.</p>



<h3 id="h-sputnik-1">Sputnik 1</h3>



<p>Sputnik 1 was the first man-made satellite to make it into space. The world, and even the Soviets, were surprised by Sputnik's success. This Soviet success worried Americans, who wanted to show the world their dominance. Sputnik-1 created the Space Race and instigated the most intensive period of space exploration to date.<br>&nbsp;</p>



<h4 id="h-launching-date">Launching Date</h4>



<p>October 4, 1957</p>



<h4 id="h-country">Country</h4>



<p>The Soviet Union.</p>



<h3 id="h-pioneer-1">Pioneer 1</h3>



<p>Just a year after Sputnik-1 reached space, NASA had its first rocket launch. Pioneer 1 sent a small probe into space, which ultimately failed. However, Pioneer 1 marked NASA's importance on the international stage of space exploration.<br>&nbsp;</p>



<h4 id="h-launching-date-1">Launching Date</h4>



<p>October 11, 1958</p>



<h4 id="h-launching-country">Launching Country</h4>



<p>The United States.</p>



<h3 id="h-vostok-1">Vostok-1</h3>



<p>Yuri Gagarin made history aboard Vostok-1 as the first human in outer space. The entire flight was under two hours long.<br>&nbsp;</p>



<h4 id="h-launching-date-2">Launching Date</h4>



<p>April 12, 1961</p>



<h4 id="h-launching-country-1">Launching Country</h4>



<p>The Soviet Union.</p>



<figure class="wp-block-image alignnone size-large wp-image-1886837"><img src="https://www.earth.com/wp-content/uploads/2020/12/moon-landing-60543_1280-1018x1024.jpg" alt="" class="wp-image-1886837"/><figcaption>Apollo 11 on the Moon. <a href="https://www.shutterstock.com/g/ebic">Castleski</a>/Shutterstock.com</figcaption></figure>



<h3 id="h-apollo-11">Apollo 11</h3>



<p>Even though the Soviet Union beat the United States on the first satellite and the first human in space, NASA ultimately won the Space Race by getting the first human on the moon. Apollo 11 brought Niel Armstrong to the moon where he said "That's one small step for man, one giant leap for mankind."<br>&nbsp;</p>



<h4 id="h-launching-date-3">Launching Date</h4>



<p>July 16, 1969</p>



<h4 id="h-launching-country-2">Launching Country</h4>



<p>The United States.</p>



<h3 id="h-space-shuttle-columbia">Space Shuttle Columbia</h3>



<p>The Space Shuttle Columbia was the first reusable spaceship. The Columbia survived 27 separate rocket launches between 1981 and 2003. These two dozen trips into space provided humanity with valuable scientific discoveries. Tragically, the Space Shuttle Columbia disintegrated upon re-entry to Earth on February 1st, 2003, killing all seven pilots on board.<br>&nbsp;</p>



<h4 id="h-launching-date-4">Launching Date</h4>



<p>Columbia's first launch was on April 12, 1981.</p>



<h4 id="h-launching-country-3">Launching Country</h4>



<p>The United States.</p>



<figure class="wp-block-image alignnone wp-image-1886838 size-large"><img src="https://www.earth.com/wp-content/uploads/2020/12/challenger-62908_1920-1024x829.jpg" alt="rocket explosion" class="wp-image-1886838"/><figcaption>The smoke from the explosion of the Space Shuttle Challenger. <a href="https://www.shutterstock.com/g/everett">Everett Collection</a>/Shutterstock.com</figcaption></figure>



<h3 id="h-space-shuttle-challenger">Space Shuttle Challenger</h3>



<p>The failed launch of the Challenger is perhaps the most famous rocket launch of all time. Just seconds into its flight, the entire rocket blew up in the sky, killing seven crew members and leaving the world stunned. The Challenger flew nine successful missions before exploding, where it carried parts of the <a href="https://www.esa.int/Science_Exploration/Human_and_Robotic_Exploration/Space_Shuttle/Spacelab" target="_blank" rel="noopener noreferrer">European Spacelab</a> into space. Fun fact: There were only six space shuttles in total!<br>&nbsp;</p>



<h4 id="h-launching-date-5">Launching Date</h4>



<p>Jan 28, 1986</p>



<h4 id="h-launching-country-4">Launching Country</h4>



<p>The United States.</p>



<h3 id="h-mars-pathfinder">Mars Pathfinder</h3>



<p>The Mars Pathfinder rocket launched the first Mars rover into space. This robot sent back over 16,000 photos of Mars along with a chemical analysis of Martian soil.<br>&nbsp;</p>



<h4 id="h-launching-date-6">Launching Date</h4>



<p>December 4 1996</p>



<h4 id="h-launching-country-5">Launching Country</h4>



<p>The United States, Europe, Russia</p>



<figure class="wp-block-image alignnone size-large wp-image-1886839"><img src="https://www.earth.com/wp-content/uploads/2020/12/space-walk-991_1280-1024x678.jpg" alt="" class="wp-image-1886839"/><figcaption>Astronauts on a spacewalk on the International Space Station. <a href="https://www.shutterstock.com/g/creativeforce">Creative Force Studio</a>/Shutterstock.com</figcaption></figure>



<h3 id="h-expedition-1">Expedition 1</h3>



<p>Expedition 1 send the first group of people to live on International Space Station. They lived at the space station for 136 days. Ever since they set foot inside the station in the year 2000, there have been humans on the ISS.<br>&nbsp;</p>



<h4 id="h-launching-date-7">Launching Date</h4>



<p>November 2nd, 2000</p>



<h4 id="h-launching-country-6">Launching Country</h4>



<p>The United States</p>



<h2 id="h-the-future-of-rocketry">The Future of Rocketry</h2>



<p>To reach further into space, humans must create a type of power that is more efficient than the combustion that is currently used in rockets. Successful implementation of nuclear fusion and fission would be immense breakthroughs that would propel spacecraft beyond our solar system. NASA also plans to build a <a href="https://www.earth.com/earthpedia-articles/space-exploration-progress-impact-forecast/" target="_blank" rel="noopener noreferrer">staging area in space</a> to launch deep space missions.</p>



<p>In the meantime, <a href="https://www.earth.com/earthpedia-articles/top-3-biggest-private-space-companies/" target="_blank" rel="noopener noreferrer">private companies</a> plan to begin space tourism for those who can afford the tickets.</p>



<p>Check us out on <a href="https://www.earth.com/earthsnap/">EarthSnap</a>, a free app brought to you by Eric Ralls and Earth.com.</p>

What Is a Rocket? + Most Famous Launches

That humans have made it to space is a profound,...

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<p>Today’s <strong>Video of the Day</strong> from the <a href="https://www.esa.int/">European Space Agency</a> features Nushagak Bay, a large estuary in southwest Alaska. Nushagak runs mainly north to south and exits in Bristol Bay, a large body of water in the Bering Sea.</p>



<p>"The bay is primarily fed by the Nushagak River, which begins in the Alaska Range and flows southwest approximately 450 km. The bay is also fed by several additional rivers including the Wood, Igushik, Snake and Weary rivers," says ESA.</p>



<p>"The dark colors of the Nushagak River are most likely due to tannins or lignins (chemical substances found in plants). Tannins and lignins from roots, leaves, seeds, bark and soil can leach into the water and give it a brown or even black colour. The sediments then flow southwards where it is mixed with the bluer waters of the bay."</p>



<p><em>Video/ Image Credit: ESA</em></p>



<p><em>-</em><em>--</em></p>



<p><em>By </em><a href="http://csexton@earth.com"><em>Chrissy Sexton</em></a><em>, </em><a href="https://www.earth.com/staff/"><em>Earth.com</em></a><em> Staff Writer</em></p>

Nushagak Bay in southwest Alaska

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<p>Today's <strong>Video of the Day</strong> from the <a href="https://www.acs.org/">American Chemical Society</a> (ACS) reveals that proteins on flu viruses are actually flexible, tilting and waving in a “breath-like” motion. According to the experts, these proteins could be used to better defend against the flu.</p>



<p>"The main antigenic targets of influenza virus are two surface glycoproteins, hemagglutinin (HA) and neuraminidase (NA). Whereas the structural and dynamical properties of both glycoproteins have been studied previously, the understanding of their plasticity in the whole-virion context is fragmented," wrote the researchers.</p>



<p>To investigate, the team conducted detailed simulations of the influenza A H1N1 virion, or the swine flu. The experts concluded that the visualizations show many new vulnerable states of flu viruses, which could improve future vaccines and antiviral drugs.</p>



<p><em>Video/ Image Credit: American Chemical Society&nbsp;</em></p>



<p><em>-</em><em>--</em></p>



<p><em>By </em><a href="mailto:csexton@earth.com"><em>Chrissy Sexton</em></a><em>, </em><a href="https://www.earth.com/staff/"><em>Earth.com</em></a><em> Editor</em></p>



<p>Check us out on <a href="https://www.earth.com/earthsnap/">EarthSnap</a>, a free app brought to you by Eric Ralls and Earth.com.</p>

Flu viruses are more flexible than expected

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<p>Today’s <strong>Video of the Day</strong> from the <a href="https://www.esa.int/">European Space Agency</a> features Lake Trasimeno, which is located west of Perugia in central Italy. It is the fourth largest lake in the country. While Trasimeno’s water level varies, it has a maximum depth of approximately six meters.&nbsp;</p>



<p>"In this Copernicus Sentinel-2 image, captured on 6 August 2022, the lake’s emerald green colour is likely due to the presence of phytoplankton. Streaks in the water, particularly visible in the west, indicate the presence of soil and sediments which have been stirred up by winds. Dark colored waters in the southern part of the lake indicate a presence of submerged and floating macrophytes (aquatic plants) as well as algae," says ESA.</p>



<p>"Surrounded by hills on three sides, Trasimeno is subject to heavy storms created by winds, especially from the north and west. There are three islets in the lake: Maggiore, Minore and Polvese (the largest). The lake’s shores are sparsely inhabited with only two popular villages: Castiglione del Lago and Passignano sul Trasimeno."</p>



<p>"Italy is experiencing its worst drought in 70 years which has affected drinking water supplies, hydroelectric power and agricultural production. High temperatures, hot winds and lack of rainfall are the main causes of drought in the Umbrian region which saw Lake Trasimeno’s drop 1.3 m, reaching the limit of the hydrometric zero in July 2022."</p>



<p><em>Video/Image Credit: ESA&nbsp;</em></p>



<p><em>-</em><em>--</em></p>



<p><em>By </em><a href="http://csexton@earth.com"><em>Chrissy Sexton</em></a><em>, </em><a href="https://www.earth.com/staff/"><em>Earth.com</em></a><em> Staff Writer</em></p>

Lake Trasimeno in Central Italy

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<p>Today's <strong>Video of the Day</strong> from the <a href="https://www.acs.org/">American Chemical Society</a> describes a new self-powered nanosensor that can instantly detect mercury contamination with the tap of a finger.&nbsp;</p>



<p>The oxidized form of mercury can be harmful when it is ingested through contaminated water or food. This makes it necessary for experts to develop sensors that can quickly and accurately detect the presence of mercury.&nbsp;</p>



<p>Zong-Hong Lin and colleagues have now created a triboelectric nanosensor (TENS) that can detect mercury by simply by touching a sample. According to the researchers, their TENS could serve as the basis for similar devices to safely and remotely monitor other pollutants.</p>



<p><em>Video Credit: American Chemical Society&nbsp;</em></p>



<p><em>-</em><em>--</em></p>



<p><em>By </em><a href="mailto:csexton@earth.com"><em>Chrissy Sexton</em></a><em>, </em><a href="https://www.earth.com/staff/"><em>Earth.com</em></a><em> Editor</em></p>



<p>Check us out on <a href="https://www.earth.com/earthsnap/">EarthSnap</a>, a free app brought to you by Eric Ralls and Earth.com.</p>

Detecting mercury contamination with the tap of a finger

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<p>Today’s <strong>Video of the Day</strong> from the <a href="https://www.acs.org/">American Chemical Society</a> explores the ability of salt to transform the way that foods and beverages taste. Salt is known to cover up undesirable flavors, such as bitterness in coffee or beer, but how exactly does sodium chloride change the taste of other compounds?</p>



<p>One previous study showed that, not only does salt suppress bitterness, but also enhances sweetness and sourness. Another study revealed that bitterness reduction by salt seems to be happening at the tongue receptor level as well as in the brain.&nbsp;</p>



<p>While it is known that salt taste is mediated by the presence of sodium channels in the form of taste buds, experts believe that there is also an unknown receptor responsible for how we taste salt that has not yet been identified.&nbsp;</p>



<p><em>Video Credit: ACS Reactions</em></p>



<p><em>-</em><em>--</em></p>



<p><em>By </em><a href="mailto:csexton@earth.com"><em>Chrissy Sexton</em></a><em>, </em><a href="https://www.earth.com/staff/"><em>Earth.com</em></a><em> Editor</em></p>



<p>Check us out on <a href="https://www.earth.com/earthsnap/">EarthSnap</a>, a free app brought to you by Eric Ralls and Earth.com.</p>

How does salt makes things taste better?

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<p>Today’s <strong>Video of the Day</strong> from the <a href="https://www.esa.int/">European Space Agency</a> features Santiago, the capital city of Chile. The city is located in the center of the Santiago Metropolitan Region, which has a population of about eight million people.&nbsp;</p>



<p>'The weather of Santiago resembles the Mediterranean climate with dry and warm summers with temperatures reaching up to 35°C (from October to March) and cool and humid winters that can drop to 0°C (from April to September)."</p>



<p>"The city lies in the centre of the country’s central valley around 80 km from the Pacific Ocean to the west and borders Argentina to the east. A tiny part of Argentina is visible in the top-right corner of the image where the mountain crest of the Andes Mountains acts as a divider between the two countries," says ESA.</p>



<p><em>Video/ Image Credit: ESA</em></p>



<p><em>-</em><em>--</em></p>



<p><em>By </em><a href="mailto:csexton@earth.com"><em>Chrissy Sexton</em></a><em>, </em><a href="https://www.earth.com/staff/"><em>Earth.com</em></a><em> Editor</em></p>



<p>Check us out on <a href="https://www.earth.com/earthsnap/">EarthSnap</a>, a free app brought to you by Eric Ralls and Earth.com.</p>

Santiago, Chile in South America

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Spiral,Galaxy,,Illustration,Of,Milky,Way

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<p>Astronomers at <a href="https://www.jhu.edu/">Johns Hopkins University</a> have created an interactive map of the universe, including the actual position and real colors of 200,000 galaxies. The map allows the public to access data that was previously only available to scientists.</p>



<p>The map was developed using data collected by the Sloan Digital Sky Survey. For over two decades, a telescope in New Mexico was aimed at slightly different locations to capture the night sky.&nbsp;</p>



<p>"Growing up I was very inspired by astronomy pictures, stars, nebulae and galaxies, and now it's our time to create a new type of picture to inspire people," said map creator Brice Ménard, a professor at Johns Hopkins. "Astrophysicists around the world have been analyzing this data for years, leading to thousands of scientific papers and discoveries. But nobody took the time to create a map that is beautiful, scientifically accurate, and accessible to people who are not scientists. Our goal here is to show everybody what the universe really looks like."</p>



<p>"In this map, we are just a speck at the very bottom, just one pixel. And when I say we, I mean our galaxy, the Milky Way which has billions of stars and planets. We are used to seeing astronomical pictures showing one galaxy here, one galaxy there or perhaps a group of galaxies. But what this map shows is a very, very different scale."</p>



<p>"From this speck at the bottom, we are able to map out galaxies across the entire universe, and that says something about the power of science."</p>



<p>The <a href="https://mapoftheuniverse.net/">interactive map</a> is available online, where it can be downloaded for free.</p>



<p><em>Video Credit: Johns Hopkins&nbsp;</em></p>



<p><em>-</em><em>--</em></p>



<p><em>By </em><a href="mailto:csexton@earth.com"><em>Chrissy Sexton</em></a><em>, </em><a href="https://www.earth.com/staff/"><em>Earth.com</em></a><em> Editor</em></p>



<p>Check us out on <a href="https://www.earth.com/earthsnap/">EarthSnap</a>, a free app brought to you by Eric Ralls and Earth.com.</p>

Interactive map of the universe includes 200,000 galaxies

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<p>Lesotho: Africa's "Kingdom in the Sky" Today’s <strong>Video of the Day</strong> from the <a href="https://www.esa.int/">European Space Agency</a> features northwest Lesotho in South Africa.</p>



<p>According to ESA, Lesotho is the only nation in the world that lies completely above 1,000 m in elevation. The country is famous for its tall mountains and narrow valleys, and is known as Africa's "Kingdom in the Sky."</p>



<p>Out of a population of around two million people, about 80 percent live in rural areas. More than 75 percent of these people are engaged in <a href="https://www.earth.com/news/climate-change-will-have-a-global-impact-on-agriculture/">agriculture</a>, including rainfed cereal production and animal grazing.&nbsp;</p>



<p>ESA reports that the country’s agricultural system faces a growing number of issues, with climate-related vulnerabilities such as drought, floods and extreme temperatures occurring more frequently. </p>



<p>Diamonds are amongst the minerals found in the mountains. Indeed, Lesotho can truly be called the Kingdom in the Sky. Beautiful, culturally rich, safe, affordable, and easily accessible from Durban and Johannesburg, mountainous Lesotho is a vastly underrated travel destination. the Kingdom of Lesotho (Sotho: 'Muso oa Lesotho) is an enclaved country in southern Africa. It is just over 30,000 km2 (11,583 sq mi) in size and has a population of around 2 million.</p>



<p><em>Video Credit: ESA&nbsp;&nbsp;</em></p>



<p><em>-</em><em>--</em></p>



<p><em>By </em><a href="mailto:csexton@earth.com"><em>Chrissy Sexton</em></a><em>, </em><a href="https://www.earth.com/staff/"><em>Earth.com</em></a><em> </em>Staff Writer </p>



<p>Check us out on <a href="https://www.earth.com/earthsnap/">EarthSnap</a>, a free app brought to you by Eric Ralls and Earth.com.</p>

Lesotho: Africa's "Kingdom in the Sky"

[sendtonews key="uV9Lh2fQbV-1760058-12187" type="single"] Lesotho: Africa's "Kingdom in the Sky" Today’s...

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<p>Today's <strong>Video of the Day</strong> from the <a href="https://www.esa.int/">European Space Agency</a> features Dublin, the capital and largest city of Ireland. Beyond its pub culture, Dublin is known as a modern culinary destination and a UNESCO City of Literature.</p>



<p>"Dublin is located near the midpoint of Ireland’s east coast in the province of Leinster. The city, which covers an area of around 115 square kilometers, is bordered by the Dublin Mountains, a low mountain range to the south, and is surrounded by flat farmland to the north and west," says ESA.</p>



<p>"The city straddles the River Liffey, which rises in the Wicklow Mountains and flows around 80 kilometers eastwards through the city of Dublin, in which it is canalised and bordered with quays. It then empties into Dublin Bay, an arm of the Irish Sea."</p>



<p>Dublin has an abundance of green spaces, including one of the largest enclosed public parks in any European capital city. Phoenix Park, which was originally formed as a royal hunting park in the 1660s, includes 707 hectares of green space.</p>



<p><em>Video Credit: ESA&nbsp;</em></p>



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<p><em>By </em><a href="mailto:csexton@earth.com"><em>Chrissy Sexton</em></a><em>, </em><a href="https://www.earth.com/staff/"><em>Earth.com</em></a><em> Editor</em></p>



<p>Check us out on <a href="https://www.earth.com/earthsnap/">EarthSnap</a>, a free app brought to you by Eric Ralls and Earth.com.</p>

The city of Dublin on Ireland's east coast

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<p>Today's <strong>Video of the Day</strong> from the <a href="https://www.esa.int/">European Space Agency</a> features the province of Zaragoza in northeast Spain. The image was captured by the Copernicus Sentinel-2 mission.</p>



<p>"Together with the provinces of Huesca and Teruel, Zaragoza formed the old kingdom of Aragon. Its capital, also called Zaragoza (not visible in this image) is home to around half of Aragon’s population," says ESA.</p>



<p>"The Ebro River can be seen winding its way through the province from west to east in this image. Between its source in the Cantabrian Mountains in the northwest and its delta on the Mediterranean coast, the Ebro River is fed by more than 200 tributaries as it flows 910 km across much of northern Spain."</p>



<p>Since rainfall is very scarce in this region, irrigation in the Ebro basin is critically important. In the valleys surrounding the Ebro River, many fields are used for growing crops such as corn, wheat, and barley.</p>



<p><em>Video/ Image Credit: ESA</em></p>



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<p><em>By </em><a href="mailto:csexton@earth.com"><em>Chrissy Sexton</em></a><em>, </em><a href="https://www.earth.com/staff/"><em>Earth.com</em></a><em> Editor</em></p>



<p>Check us out on <a href="https://www.earth.com/earthsnap/">EarthSnap</a>, a free app brought to you by Eric Ralls and Earth.com.</p>

The province of Zaragoza in northeast Spain

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<p>Today’s <strong>Video of the Day</strong> from <a href="https://earthobservatory.nasa.gov/">NASA Earth Observatory</a> reveals the evolution of the Columbia Glacier in southeastern Alaska. Columbia is among the fastest shrinking glaciers in the world, and the video documents its rapid retreat over the years.&nbsp;</p>



<p>Columbia Glacier is a large, multi-branched calving glacier that flows out of the Chugach Mountains to the Prince William Sound.&nbsp;</p>



<p>According to USGS, Columbia had a long history of stability prior to 1980, with a length 41 miles, and small, short-lived advances or retreats.</p>



<p>In the years since 1980, however, satellite images have captured Columbia’s alarming retreat. By using false-color images, scientists can distinguish between snow and ice, open water, vegetation, and rocky debris on the glacier’s surface.</p>



<p>The series of false-color images featured in today's video were acquired over the span of 35 years. You can see that by 2021, the glacier’s main branch had retreated about 15 miles from its initial position.</p>



<p>The Columbia Glacier has also lost more than 50 percent of its volume, mostly due to calving. <a href="https://www.earth.com/video/nasa-reveals-3d-visual-of-an-atmospheric-river/">NASA</a> reports that while climate change likely started the retreat, mechanical processes kept the disintegration going.</p>



<p>The NASA images are provided by Jesse Allen, Robert Simmon, Joshua Stevens, and Lauren Dauphin using data from Landsat satellites, from the U.S. Geological Survey, and data from MODIS on NASA’s Terra satellite. The structure of Columbia’s moraine played a large role in the stability of the glacier before 1980. </p>



<p>Like other tidewater glaciers, the Columbia built up a moraine over time, and the mixture of ice and rock functioned like a dam keeping out the sea. It was supported on one end by the shoreline and by the underwater terminal moraine at the other.</p>



<p><em>Video Credit: NASA Earth Observatory/&nbsp; NASA’s Scientific Visualization Studio</em></p>



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<p><em>By </em><a href="mailto:csexton@earth.com"><em>Chrissy Sexton</em></a><em>, </em><a href="https://www.earth.com/staff/"><em>Earth.com</em></a><em> Editor</em></p>



<p>Check us out on <a href="https://www.earth.com/earthsnap/">EarthSnap</a>, a free app brought to you by Eric Ralls and Earth.com.</p>

The rapid retreat of the Columbia Glacier

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<p>Today’s <strong>Video of the Day</strong> from the <a href="https://www.esa.int/">European Space Agency</a> features the Pyrenees Mountains, which form a natural boundary between France and Spain in southwest Europe.</p>



<p>The mountain range is 430 kilometers in length. It stretches from the Mediterranean Sea on the east to the Atlantic Ocean on the west.</p>



<p>At an elevation of 3404 meters, Pico de Aneto is the highest mountain peak in the Pyrenees, and the third-highest peak in Spain. Pico de Aneto is located in the Posets-Maladeta Natural Park, which spans more than 82,000 acres.&nbsp;</p>



<p>"Geological studies have revealed that the Pyrenees Mountains have been around for longer than the Alps, with their sediments first deposited in coastal basins during the Paleozoic and Mesozoic eras," reports ESA.</p>



<p>"The entire mountain range formed due to the upwelling of large sedimentary rocks by the collision of the Iberian and the Eurasian plate around 100 to 150 million years ago, followed by intense erosion from ice and water."</p>



<p>The western Pyrenees receive more precipitation due to moisture blowing in from the Atlantic Ocean. The mountain range contains many lakes, several small glaciers, and some of the highest waterfalls in Europe.</p>



<p><em>Video &amp; Image Credit: ESA</em></p>



<p><em>-</em><em>--</em></p>



<p><em>By </em><a href="mailto:csexton@earth.com"><em>Chrissy Sexton</em></a><em>, </em><a href="https://www.earth.com/staff/"><em>Earth.com</em></a><em> Editor</em></p>



<p>Check us out on <a href="https://www.earth.com/earthsnap/">EarthSnap</a>, a free app brought to you by Eric Ralls and Earth.com.</p>

The Pyrenees Mountains in southwest Europe

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Earth,Like,Exoplanet,3d,Render

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<p>Today's <strong>Video of the Day</strong> from <a href="https://www.nasa.gov/goddard">NASA Goddard</a> describes two exoplanets that are orbiting a star 218 light-years away. A team of researchers led by the University of Montreal has found evidence that these planets are "water worlds."</p>



<p>The experts used data from NASA’s Hubble and Spitzer Space Telescopes. They discovered that exoplanets Kepler-138 c and Kepler-138 could be composed largely of water.</p>



<p>"We previously thought that planets that were a bit larger than Earth were big balls of metal and rock, like scaled-up versions of Earth, and that's why we called them super-Earths," explained study co-author Björn Benneke.&nbsp;</p>



<p>"However, we have now shown that these two planets, Kepler-138 c and d, are quite different in nature and that a big fraction of their entire volume is likely composed of water. It is the best evidence yet for water worlds, a type of planet that was theorized by astronomers to exist for a long time."</p>



<p><em>Video Credit: NASA Goddard</em></p>



<p><em>Image Credit: NASA, ESA, and Leah Hustak (STScI)</em></p>



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<p><em>By </em><a href="mailto:csexton@earth.com"><em>Chrissy Sexton</em></a><em>, </em><a href="https://www.earth.com/staff/"><em>Earth.com</em></a><em> Editor</em></p>



<p>Check us out on <a href="https://www.earth.com/earthsnap/">EarthSnap</a>, a free app brought to you by Eric Ralls and Earth.com.</p>

Two distant planets may be "water worlds"

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<p>Satellites reveal how Earth's systems are interconnected Today’s <strong>Video of the Day</strong> from <a href="https://www.nasa.gov/goddard">NASA Goddard</a> describes Earth’s interconnected systems, and how this network is affected by rising temperatures.&nbsp;</p>



<p>During 2020, average global temperatures matched the hottest year on record. The hurricane season was also record-breaking, with many of the storms intensifying at extraordinary speeds. Hot water in the ocean is fuel for hurricanes. The satellite data shows that it's all one interconnected system showing how  Satellites reveal how Earth's systems are interconnected.</p>



<p>According to NASA, dust swept up from Northern Africa plays a major role in the formation of hurricanes, and is also a key source of fertilization in the Amazon rainforest. As a result of<a href="https://www.earth.com/news/seagrass-wasting-disease-is-fueled-by-climate-change/"> climate</a> change, dust plumes are expected to decline, which will have an effect on vegetation far away.&nbsp;</p>



<p>Images from Earth-observing satellites show how the world’s plant life is affected by natural disasters, fires, and deforestation. Satellites also reveal how widespread changes in vegetation impact waterways,&nbsp; the climate, air quality. Satellites communicate by using radio waves to send signals to the antennas on the Earth. "Earth From Space" is a groundbreaking two-hour special that reveals a spectacular new space-based vision of our planet. </p>



<p><em>Video Credit: NASA Goddard&nbsp;</em></p>



<p><em>-</em><em>--</em></p>



<p><em>By </em><a href="mailto:csexton@earth.com"><em>Chrissy Sexton</em></a><em>, </em><a href="https://www.earth.com/staff/"><em>Earth.com</em></a><em> Editor</em></p>



<p>Check us out on <a href="https://www.earth.com/earthsnap/">EarthSnap</a>, a free app brought to you by Eric Ralls and Earth.com.</p>

Satellites reveal how Earth's systems are interconnected

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<p>Today’s <strong>Video of the Day</strong> from the <a href="https://welcome.miami.edu/">University of Miami</a> Rosenstiel School of Marine and Atmospheric Science explores how changes in water temperatures have affected tiger shark habitats and movements in the North Atlantic Ocean. The study reveals that rising temperatures have caused the sharks to shift toward the poles over the past 40 years.</p>



<p>“Tiger shark annual migrations have expanded poleward, paralleling rising water temperatures,” explained study lead author Neil Hammerschlag. “These results have consequences for tiger shark conservation, since shifts in their movements outside of marine protected areas may leave them more vulnerable to commercial fishing.”</p>



<p>The researchers analyzed nine years of tracking data from satellite-tagged tiger sharks, combined with four decades of conventional tag and recapture data provided by National Oceanic and Atmospheric Administration (NOAA) Cooperative Shark Tagging Program.</p>



<p>The experts found that during the last decade of record heat, for every one-degree Celsius increase in water temperatures, tiger sharks migrated further poleward by over 400 kilometers. They also migrated two weeks earlier than usual to waters off the northeastern coast of the United States.</p>



<p>“Given their role as apex predators, these changes to tiger shark movements may alter predator-prey interactions, leading to ecological imbalances, and more frequent encounters with humans,” concluded Professor Hammerschlag.</p>



<p><em>Video Credit: University of Miami Rosenstiel School of Marine and Atmospheric Science</em></p>



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<p><em>By </em><a href="mailto:csexton@earth.com"><em>Chrissy Sexton</em></a><em>, </em><a href="https://www.earth.com/staff/"><em>Earth.com</em></a><em> Editor</em></p>



<p>Check us out on <a href="https://www.earth.com/earthsnap/">EarthSnap</a>, a free app brought to you by Eric Ralls and Earth.com.</p>

Tiger sharks are shifting poleward as temperatures rise

Today’s Video of the Day from the University of Miami...

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<p>Today’s <strong>Video of the Day</strong> from the <a href="https://www.esa.int/">European Space Agency</a> is focused on the melt ponds that emerge during the spring and summer on the Greenland Ice Sheet, which is the largest ice mass in the northern hemisphere.</p>



<p>"Melt ponds are vast pools of open water that form on both sea ice and ice sheets and are visible as turquoise-blue pools of water in this Copernicus Sentinel-2 image," says ESA.</p>



<p>"When snow and ice melts atop glaciers, water flows in channels and streams and collects in depressions on the surface. These melt ponds can speed up the melting of the surrounding ice since they greatly reduce the ice’s ability to reflect sunlight."</p>



<p>"This can create a positive feedback where an increasing number of melt ponds absorb more heat which causes ice cover to melt even faster."</p>



<p>According to ESA, Greenland has been hit with a late-season heatwave that began in early September. This caused the type of melt event that usually occurs in the middle of summer.</p>



<p>"In a recent paper published in Nature Climate Change, scientists found that major sea-level rise from the melting of the Greenland ice cap is now ‘inevitable’ even if the burning of fossil fuels were to halt overnight," says ESA. "Using satellite observations of Greenland ice loss and ice cap from 2000 to 2019, the team found the losses will lead to a minimum rise of 27 cm regardless of climate change."</p>



<p><em>Video Credit: ESA&nbsp;</em></p>



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<p><em>By </em><a href="mailto:csexton@earth.com"><em>Chrissy Sexton</em></a><em>, </em><a href="https://www.earth.com/staff/"><em>Earth.com</em></a><em> Editor</em></p>



<p>Check us out on <a href="https://www.earth.com/earthsnap/">EarthSnap</a>, a free app brought to you by Eric Ralls and Earth.com.</p>

Melt ponds on the Greenland Ice Sheet

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<p>Today’s <strong>Video of the Day</strong> from the <a href="https://www.esa.int/">European Space Agency</a> describes a new map of Mars that is providing insight into the planet’s watery past. The map also reveals where future missions could safely land on Mars.&nbsp;</p>



<p>The map has been created over the last decade using observations of water-rich rocks and mineral deposits. The images were captured by ESA’s Mars Express and NASA’s Mars Reconnaissance Orbiter.</p>



<p>"A big surprise is the prevalence of these minerals, with the map revealing hundreds of thousands of water-affected locations in the oldest parts of the planet," says ESA. "The new data will help answer exciting questions about Mars’ climate history, whether water was globally persistent or confined to short, intense episodes, and whether the conditions were ever suitable for life."</p>



<p>"Specifically, the map shows the locations and abundances of aqueous minerals. These are from rocks that have been chemically altered by the action of water in the past, and have typically been transformed into clays and salts."</p>



<p>According to John Carter of the Institut d’Astrophysique Spatiale (IAS), our collective understanding of Mars has been oversimplified. He explained that planetary scientists have tended to think that only a few types of clay minerals on Mars were created during its wet period, then as the water gradually dried up, salts were produced across the planet.</p>



<p>The new map shows that the composition of Mars is much more complicated than what we thought. For example, while many salts formed after Martian clays, there are some salts that are presumed to be older than some of the clays.&nbsp;</p>



<p>“The evolution from lots of water to no water is not as clear cut as we thought, the water didn’t just stop overnight. We see a huge diversity of geological contexts, so that no one process or simple timeline can explain the evolution of the mineralogy of Mars. That’s the first result of our study. The second is that if you exclude life processes on Earth, Mars exhibits a diversity of mineralogy in geological settings just as Earth does,” said Carter.</p>



<p><em>Video Credit: ESA</em></p>



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<p><em>By </em><a href="mailto:csexton@earth.com"><em>Chrissy Sexton</em></a><em>, </em><a href="https://www.earth.com/staff/"><em>Earth.com</em></a><em> Editor</em></p>



<p>Check us out on <a href="https://www.earth.com/earthsnap/">EarthSnap</a>, a free app brought to you by Eric Ralls and Earth.com.</p>

The history of Mars is much more complex than we thought

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<p>Today's <strong>Video of the Day</strong> from the <a href="https://www.stowers.org/">Stowers Institute for Medical Research</a> describes how cavefish adapted to a sedentary lifestyle over tens of thousands of years. </p>



<p>The experts found that the muscle metabolism of cavefish has been genetically reprogrammed over time. As a result, the animals have experienced major changes in their morphology and behavior. Despite these changes, however, the cavefish remain healthy and fit.</p>



<p>The research may provide new clues about the evolutionary consequences of prolonged physical inactivity in humans.&nbsp;</p>



<p>“It’s no surprise that people are moving less and less as technology has advanced,” said Rohner. “With cavefish, we have a unique system where we can study what might happen if people remained couch potatoes over very, very long periods of time.”</p>



<p><em>Video Credit: Stowers Institute for Medical Research</em></p>



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<p><em>By </em><a href="mailto:csexton@earth.com"><em>Chrissy Sexton</em></a><em>, </em><a href="https://www.earth.com/staff/"><em>Earth.com</em></a><em> Editor</em></p>



<p>Check us out on <a href="https://www.earth.com/earthsnap/">EarthSnap</a>, a free app brought to you by Eric Ralls and Earth.com.</p>

Cavefish are healthy despite their sedentary lifestyle

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<p>Today’s <strong>Video of the Day</strong> from <a href="https://earthobservatory.nasa.gov/">NASA Earth Observatory</a> some of the most incredible waves in the world, as seen by Landsat satellites.</p>



<p>"With more than 370,000 miles of coastline on Earth, there are plenty of places where epic waves build up, curl over, and hurtle toward the shore.- much to the thrill of surfers," says NASA. "There are some places where these waves are so magnificent that they can be seen from space."</p>



<p>"With the broad perspective of satellites, we can see how these iconic waves develop into the world’s tallest, longest, fastest, and heaviest."</p>



<p><em>Video Credit: NASA Earth Observatory&nbsp;</em></p>



<p><em>-</em><em>--</em></p>



<p><em>By </em><a href="mailto:csexton@earth.com"><em>Chrissy Sexton</em></a><em>, </em><a href="https://www.earth.com/staff/"><em>Earth.com</em></a><em> Editor</em></p>



<p>Check us out on <a href="https://www.earth.com/earthsnap/">EarthSnap</a>, a free app brought to you by Eric Ralls and Earth.com.</p>

Satellites capture the world's biggest and fastest waves

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<p>Today’s <strong>Video of the Day</strong> from the <a href="https://www.esa.int/">European Space Agency</a> describes why satellite images and measurements of our planet have become "essential to our survival, offering a new outlook of our world."&nbsp;</p>



<p>Rising sea levels pose one of the biggest societal threats associated with climate change. According to ESA, satellite altimeter missions such as Copernicus Sentinel-6 are essential in monitoring global and regional changes in sea level.</p>



<p>"Unbeknown to many, the island of Crete, Greece, plays an important role in the Copernicus satellite altimetry constellation and on an international stage," reports ESA.</p>



<p>"Satellite altimetry data have to be continuously monitored at the ESA’s Permanent Facility for Altimetry Calibration where different techniques have pioneered the use of transponders to provide the best measurements to validate satellite altimeters in space soon after launch."</p>



<p>Dr. Craig Donlon explains that, by understanding planet Earth through satellite measurements, we are able to find evidence of change.&nbsp;</p>



<p><em>Video Credit: European Space Agency&nbsp;</em></p>



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<p><em>By </em><a href="http://csexton@earth.com"><em>Chrissy Sexton</em></a><em>, </em><a href="https://www.earth.com/staff/"><em>Earth.com</em></a><em> Staff Writer</em></p>

Satellites have become essential to our survival

[sendtonews key="761m2QQvR1-2035772-12187" type="single"] Today’s Video of the Day from the...